FRCA anatomy Flashcards
Where in the skull is the foramen magnum found? (1 mark)
Posterior cranial fossa; basilar part of the occipital bone
Name four structures that pass through the foramen magnum (4 marks)
- Osteo-ligamentous structures:
• Tip of odontoid process
• Ligaments (apical ligament, superior band of cruciate ligament, tectorial membrane) - Neurovascular structures:
• Lower end of medulla (with meninges)
• Cerebellar tonsils (variant)
• Spinal roots of CN 11 (either side, within subarachnoid space) • Vertebral arteries
• Anterior and posterior spinal arteries (within subarachnoid space) (Anterior/posterior atlanto-occipital membranes attach to the margin of foramen magnum)
*The osteo-ligamentous structures lie anterior to the alar ligaments, and the neurovascular structures lie posteriorly
Name three types of brain herniation (3 marks)
- Subfalcine (cingulate),A
- uncal (transtentorial) D and
- tonsillar (cerebellar) E
(Others: transcalvarial, central transtentorial, upward transtentorial)
○ CN 3 palsy: dilated pupil (initially, loss of parasympathetic supply to pupil), ‘down and out’ (loss of supply to superior/medial inferior rectus and inferior oblique)
° CN 6 palsy: failure of lateral gaze/convergent squint (loss of supply to lateral rectus)
Why may ocular features be a false-localising sign in brain injury causing cerebellar herniation? (2 marks)
○ CN 3: may be compressed on margin of tentorium cerebelli by concurrent herniation of uncus
○ CN 6: has a long intracranial course, compressed by oedema in many intracranial locations
Describe the pathophysiological changes of tonsillar (cerebellar) herniation (aka coning) (5 marks)
Raised intracerebral pressure (ICP) results in raised mean arterial pressure (MAP) to maintain cerebral perfusion pressure
(CPP)
(CPP = MAP- ICP)
Eventually, raised ICP causes downward displacement of cerebellar tonsils
• As they pass into the foramen magnum, the lower brainstem (medulla and pons) is compressed, with resulting dysfunction of the cardiac and respiratory centres
○ Initial pontine ischaemia results in a hyperadrenergic state (to maintain brainstem perfusion)
• Cushing’s reflex (may only be present in one-third) suggests coning is imminent and describes:
* Hypertension (to maintain brainstem perfusion)
* Bradycardia (reflex baroreceptor activation due to hypertension +/midbrain activation of the parasympathetic nervous system)
* Abnormal respiration (dysfunction of respiratory centre)
After herniation/neuronal death, the loss of spinal cord sympathetic discharge results in vasodilation, bradycardia and impaired contractility (with resultant cardiovascular instability)
Other dysfunction ensues:
• Pituitary ischaemia may result in diabetes insipidus (DI)
• Hypothalamic dysfunction may lead to loss of thermoregulation (compounded by vasodilation, reduced basal metabolic rate and hypothyroidism)
• Coagulopathy (catecholamine effects on platelets, hypothermia and release of plasminogen activator due to neuronal death)
What hormone supplementation may be required in such patients if they are considered for brainstem death organ donation? (5 marks)
○ Vasopressin (to maintain cardiovascular stability and for DI, noradrenaline is generally avoided)
○ Methylprednisolone (to reduce neurogenic pulmonary oedema)
○ Thyroid hormone (to maintain cardiac function)
○ Desmopressin (if DI persists despite the use of vasopressin)
○ Insulin (to combat hyperglycaemia resulting from catecholamine release, IV dextrose used to replace water in DI and steroids)
What awake surgical procedures are permitted by the use of an axillary block?
(2 marks)
Procedures below the elbow: forearm, wrist and hand
Name the nerves targeted when performing this block and where they are found (4 marks)
- Musculocutaneous nerve (fascial plane between short head of biceps and coracobrachialis) 2. Median nerve (superolateral to the axillary artery, 9–12 o’clock position)
- Ulnar nerve (inferomedial to axillary artery, beneath axillary vein, 2–3o’clock position)
- Radial nerve (deep to axillary artery, 4–6o’clock position)
Name the nerves targeted when performing this block and where they are found (4 marks) Axillary nerve block
○ Musculocutaneous nerve (fascial plane between short head of biceps and coracobrachialis)
○ Median nerve (superolateral to the axillary artery, 9–12 o’clock position)
○ Ulnar nerve (inferomedial to axillary artery, beneath axillary vein, 2–3o’clock position)
○ Radial nerve (deep to axillary artery, 4–6o’clock position)
Regarding the musculocutaneous nerve
How can a block of this nerve be supplemented? (3 marks)
By blocking the nerve at the level of the lateral epicondyle, between the lateral border of biceps and brachioradialis, where it can be seen on ultrasound adjacent to the cephalic vein
Regarding the musculocutaneous nerve
What does it supply?
○ Motor supply: biceps, brachialis and coracobrachialis
○ Sensory supply: lateral forearm (via its continuation as the lateral cutaneous nerve of forearm)
Regarding the musculocutaneous nerve
Why may it be missed during an axillary brachial plexus block?
Because it leaves the brachial plexus in the proximal axilla (therefore lies in a separate fascial plane at this level in 70% of the population, thus it should be blocked separately)
What pattern of missed segment(s) is demonstrated in an inadequate axillary block? What areas are most likely to be spared in patients and why? What can be done to remedy this? (5 marks)
Because the block is performed at the level of the terminal branches of the brachial plexus, missed segments demonstrate a nerve territory distribution (rather than dermatomal)
°Medial side of forearm and (especially) arm, because:
○ Intercostobrachial nerve (lateral cutaneous branch of T2) supplies skin over the medial proximal arm and is not blocked
○ Medial cutaneous nerves of arm and forearm are branches of the medial cord of the brachial plexus in the axilla (before the ulnar nerve is given off) and therefore may be missed if not blocked separately
○ A subcutaneous injection of local anaesthetic in the medial proximal arm (or guided by ultrasound to target the medial cutaneous nerves of arm/forearm) can be performed
- Brachial plexus block provides superior tourniquet coverage compared to distal nerve blocks (muscle ischaemia is the main problem)– this is an important consideration for upper limb surgery, in addition to covering the surgical site
Describe a technique for performing an ultrasound-guided axillary brachial plexus block (6 marks)
Stop before you block: confirm side and site SLIMRAG*:
• Sterile procedure (wash hands, sterile gloves, sterile dressing pack)
• Light source/ultrasound IV access
• Monitoring (AAGBI minimum standard)
• Resuscitation drugs/equipment available
• Assistant (who is happy to assist with regional or general anaesthetic)
• General anaesthetic (ensure equipment/drugs available to convert if required)
- Position the patient supine, upper limb abducted and externally rotated, elbow flexed at 90°
- Clean the field with 0.5% chlorhexidine and allow to dry
- High-frequency linear array transducer applied transversely across the axilla at the junction of biceps brachii and pectoralis major (with sterile cover and gel on probe)
- Local anaesthetic to skin, then in-plane technique, blunt 22 G 50–80 mm block needle from lateral side of upper limb (can also be done out of plane)
- Block the four nerves using sonoanatomy landmarks of axillary artery and vein
- After negative aspiration slowly inject 25–30 ml of local anaesthetic, targeting each nerve
- Can augment by block of intercostobrachial +/medial cutaneous nerves of arm/ forearm
Describe the structure of the respiratory tree (10 marks)
The trachea bifurcates at the carina (plane of the sternal angle, T4–T4/5) into primary bronchi (left and right)
○ Right primary (or main) bronchus: Shorter, wider and more vertical
Azygos vein arches forwards over the bronchus
Divides into three secondary (lobar) bronchi:
• superior, middle and inferior N.B.
• Superior lobar bronchus (eparterial bronchus) is given off before the hilum of the lung
○ Left primary (or main) bronchus: Longer, narrower and more horizontal
•Passes beneath the arch of the aorta
• Passes immediately in front of (and indents) the oesophagus and descending thoracic aorta
• Divides into two secondary (lobar) bronchi: superior and inferior
○ The secondary bronchi divide into tertiary (segmental) bronchi
•These each supply a bronchopulmonary segment
: Right:
● Upper lobe: apical, anterior, posterior
● Middle lobe: medial, lateral :
● Lower lobe: apical, medial/lateral/anterior/posterior basal
○ Left:
● Upper lobe: apical, anterior, posterior, lingular (superior and inferior)
● Lower lobe: apical, medial*/lateral/anterior**/posterior basal
On average, the right side has 10 segments, left has 8–10
○ Tertiary (segmental) bronchi divide into many smaller bronchioles
Ultimately terminal bronchioles arise (1 mm diameter, no cartilage in wall)
• These give rise to respiratory bronchioles (lose respiratory epithelium)
• From these, alveolar ducts arise, and from these, alveolar sacs (which are clusters of alveoli)
• In total there are 23 divisions of the bronchial tree
• The first 17 form part of the conducting zone (finish at terminal bronchioles)
•Generations 18–23 form part of the respiratory zone (start at respiratory bronchioles)
- and ** often conjoined, hence the variable (often fewer) number of bronchopulmonary segments quoted for the left lung
Which segment(s) of which lung is most likely to be affected by aspiration of gastric contents (3 marks)
More likely on right (as right main bronchus is shorter, wider and more vertical) Depends on position:
• Supine: apical segment of right lower lobe
• Standing/sitting: posterior basal segment of right lower lobe
• Lying on right: right middle lobe or posterior segment of right upper lobe
Describe the pathophysiology of aspiration pneumonitis (3 marks)
Large particles cause acute airway obstruction +/lobar collapse and atelectasis Initial changes due to acute inflammatory response resulting from chemical irritation (aspiration pneumonitis due to haemorrhagic tracheobronchitis and pulmonary oedema)
The most likely complication is acute respiratory distress syndrome (ARDS) (infection may or may not result)
) How do you manage aspiration in a patient with a supraglottic airway device? (4 marks
- Call for help and ask surgeon to stop (only restart if patient stable +/emergency surgery)
- FiO2 to 1
- Move patient to left lateral position (if possible, head down) Suction oropharynx, down lumen (if a second-generation supraglottic airway device (SAD) is being used, suction down the gastric port +/pass a narrow bore NG tube to aspirate/decompress the stomach)
- If major airway contamination/desaturation: consider intubation, positive pressure ventilation, bronchoalveolar lavage, bronchodilators, ITU post-op
- If minimal: ensure SAD correctly placed, airway is clear and patient is adequately anaesthetised, then CXR in recovery (only antibiotics if subsequently develops infection)
Describe the boundaries of the epidural space (4 marks)
○ Extends from the foramen magnum superiorly to the sacral hiatus (sacrococcygeal membrane) inferiorly
○ Anteriorly: the vertebral bodies and intervertebral discs, covered by the posterior longitudinal ligament
○ Laterally: the pedicles and the intervertebral foramina
○ Posteriorly: the laminae of the vertebral arches, the capsules of facet joints and ligamenta flava
List the contents of the epidural space (6 marks)
○ Dural sheath/sac and contents (arachnoid mater, subarachnoid space and CSF, pia mater, spinal cord/spinal nerve roots and spinal arteries/veins)
○ Spinal nerve roots (within a sleeve of dura/arachnoid)
○ Filum terminale (beyond the termination of the dural sac at S2)
○ Vessels: (Anterior and posterior) radicular arteries
○ Internal vertebral venous plexus of Batson
○ Lymphatics
○ Loose areolar tissue* (fat content varies in direct proportion to the rest of the body)
○ Connective tissue**
*Apparently this is not uniform in distribution and exists in bands at the levels of intervertebral foramina
**A median fold of dura has been reported and would explain the occasional unilateral effect of epidural analgesia)
What structures does the Tuohy needle pass through when performing a midline epidural? (5 marks)
○ Skin
○ Subcutaneous tissue/superficial fascia ○ Supraspinous ligament
○ Interspinous ligament
○ Ligamentum flavum (ligamenta flava lie either side of the midline, between laminae of two adjacent vertebrae, but may be fused in the midline)
What are the benefits of epidural analgesia after laparotomy for malignant disease? (5 marks)
○ Short term:
•Lower pain scores
•Reduce opioid consumption (and associated side effects: respiratory depression, nausea/vomiting, immunosuppression)
•Reduced stress response, sympathetic activation and immunosuppression
•Lower transfusion requirements •Reduced incidence of respiratory failure and postoperative pneumonia
•Reduced incidence of DVT/PE
Long term:
•Reduced metastatic spread
Describe the boundaries and contents of the femoral triangle (6 marks)
○ Superior: inguinal ligament
○ Lateral: medial border of sartorius
○ Medial: medial border of adductor longus
○ Roof:fascia lata (and cribriform fascia at saphenous opening), skin/subcutaneoustissue
○ Floor: iliacus, psoas major, pectineus, adductor longus
○ Contents: Femoral nerve
• Femoral sheath, containing: :
○ Femoral artery (and branches) :
○ Femoral vein (and tributaries, including long saphenous vein) :
○ Femoral canal (containing lymphatics/deep inguinal lymph nodes, including node of Cloquet)
What is a fascia iliaca block? (2 marks)
It is a compartment block where local anaesthetic is deposited into the plane between the deep fascia overlying the iliacus muscle, where several branches of the lumbar plexus are found (femoral nerve courses through a pocket of the fascia iliaca)
○ Therefore, a large volume of local anaesthetic is required (e.g. 30 ml)
N.B. Obturator nerve (L2–4, supplying hip, medial/adductor compartment of thigh and skin of medial thigh/knee)– block is described in fascia iliaca technique, but rarely occurs as the nerve emerges on the medial side of psoas major
Describe the borders of the fascia iliaca compartment and nerves affected by the block (6 marks)
• Anterior: fascia iliaca
• Posterior: anterior surface of iliacus and psoas major/their conjoint tendon
• Medial: linea terminalis/pelvic brim
○ Lateral: inner lip of iliac crest
Nerves:
• Femoral nerve (L2–4): supplies hip, anterior/extensor compartment of this, skin of anterior thigh/medial leg and medial foot to first MTPJ
• Lateral cutaneous nerve of thigh (L2–3): supplies skin of anterolateral thigh
Describe how you would perform a fascia iliac block (6 marks)
Consent
Stop before you block: confirm side and site
SLIMRAG:
• Sterile procedure (wash hands, sterile gloves, sterile dressing pack)
• Light source/ultrasound IV access
• Monitoring (AAGBI minimum standard)
• Resuscitation drugs/equipment available
• Assistant (who is happy to assist with regional or general anaesthetic) • General anaesthetic (ensure equipment/drugs available to convert if required)
Describe the origin, course and termination of the internal jugular vein (IJV).
Make specific reference to its relationship with the carotid artery (5 marks)
Emerges through the posterior compartment of the jugular foramen as a continuation of the sigmoid sinus (Origin sometimes described as the point where it combines with the inferior petrosal sinus) Lies posterior to the internal carotid artery at the base of the skull (on the transverse process of the atlas) As it passes inferiorly in the neck, it comes to lie on the lateral side of the internal carotid artery In the lower neck, the IJV typically lies anterior/anterolateral to the common carotid artery Terminates behind the medial end of the clavicle, joining with the subclavian vein to form the brachiocephalic vein
Describe features that distinguish the jugular venous pulse (JVP) from the carotid pulse (5 marks)
○ JVP is impalpable
○ JVP has a complex waveform
○ JVP fills from the top (if IJV occluded)
○ JVP demonstrates the hepatojugular reflux (JVP will transiently rise with hepatic pressure)
○ JVP moves with respiration (normally decreasing on inspiration and rising in expiration)
List five indications for cannulating the IJV (5 marks)
○ Monitoring CVP/RV function/intravascular volume status
○ Administration of drugs that cannot be given peripherally (vasoactive drugs/inotropes, vaso-irritant drugs, e.g. potassium/amiodarone, total parenteral nutrition (TPN), some cytotoxic drugs)
○ Blood sampling due to poor vascular access
○ Insertion of pulmonary artery catheter (or its introducer sheath for large-bore IV access +/rapid fluid administration)
○ Haemodialysis/haemofiltration
○ Transvenous cardiac pacing
○ Aspiration of air embolus from right-hand side of the heart Jugular venous bulb saturation measurement
List five complications of cannulating the IJV (5 marks)
Due to needle:
• Carotid artery puncture (+/bleeding, dissection, embolus)
• Pneumothorax (or haemothorax)
• Thoracic duct injury (+/chylothorax)
• Nerve injury (e.g. CN 10, recurrent laryngeal, phrenic)
Due to line:
• Arrhythmia
• Air embolism
• Thrombosis/embolism (+/vessel stenosis)
•Infection
• Cardiac tamponade/haemopericardium 52 • Anaphylaxis has been reported from
chlorohexidine-impregnated catheters
Name the tissue layers traversed during insertion of an intercostal (chest) drain (5 marks)
○ Skin
○ Superficial fascia
○ External intercostal muscle
○ Internal intercostal muscle
○ Inner most intercostal muscle
○ Endothoracic fascia
○ Parietal pleura
Name and describe the muscles of the intercostal space (6 marks)
○ External intercostal:
•Outermost layer, fibres pass downwards and forwards from sharp inferior border of rib
• Extends from tubercle of rib (posteriorly) to costochondral junction (anteriorly)
• From the costochondral junction to the margin of the sternum, the muscle layer is replaced by the anterior intercostal membrane
○ Internal intercostal:
• Middle layer, fibres pass downwards and backwards from the costal groove
• Extends from the margin of the sternum (anteriorly) to the angle of the rib (posteriorly)
• From the angle of the rib to the tubercle, the muscle is replaced by the posterior intercostal membrane
○ Innermost layer:
• Discontinuous; separated into three parts:
1. Sternocostalis (aka transversus thoracis, anteriorly)
2. Innermost intercostals (laterally: the major part of the inner layer)
3. Subcostalis (posteriorly)
Muscle fibres from the anterior (1) and posterior (3) part of this layer cross more than one intercostal space
With the aid of a diagram, describe the structure of a spinal nerve from the T2–6 level after it has emerged from the vertebral column. State where it lies in 2the intercostal space (6 marks)
○ 31 pairs of spinal nerves, emerge from the intervertebral foramen (anterior and posterior rami of S1–4 emerge through anterior and posterior sacral foramina respectively)
○ The thoracic intercostal nerves (T2–6) divide into anterior and posterior divisions (rami)
○ The posterior ramus supplies only the muscles of the back (including erector spinae) and overlying skin to a hand’s breadth either side of the midline
○ The anterior ramus passes forwards between the middle and innermost intercostal layers
○ At the angle of the rib, a collateral branch is given off, which runs forwards in the lower part of the space and provides supply to the intercostal muscles, parietal pleura, periosteum and the periphery of the diaphragm (T7–11 only, not T2–6)
○ The main trunk of the nerve continues in the intercostal space and is mostly sensory to skin, giving a lateral cutaneous branch at the midaxillary line and ending as an anterior cutaneous branch at the edge of the sternum
Name three procedures in anaesthesia, other than intercostal drain insertion, which make use of the intercostal space (3 marks)
○ Cannula decompression of tension pneumothorax
○ Regional anaesthesia (intercostal nerve and interpleural block)
○ Ultrasound (echocardiography and lung ultrasound in intensive care)
**(Non-anaesthesia: pleural aspiration (draining fluid/air, sampling fluid), thoracotomy, lung biopsy)
Which nerve root contributes to the lumbar plexus, in what muscle is it formed and where is the muscle found? (4 marks)
○ From the anterior rami of L1–4 (sometimes with a contribution from T12)
○ It is formed within the substance of psoas major muscle (posterior third)
• Psoas major lies between the 12th rib and iliac crest on the posterior abdominal wall, anterior to the lumbar transverse processes, and lateral to the lumbar vertebral bodies/intervertebral discs and foramina
Name the branches of the lumbar plexus and their respective root
○ Iliohypogastric nerve (L1 +/T12)
○ Ilioinguinal* (L1)
○ Genitofemoral (L1–2)
○ Lateral cutaneous nerve of the thigh (L2–3)
○ Obturator nerve** (L2–4)
○ Femoral nerve (L2–4)
Name indications and contraindications for a lumbar plexus block (5 marks)
○ Indications:
• Analgesia of the ipsilateral lower limb (hip, femur, knee)
○ Absolute contraindications:
• Patient refusal
• Local anaesthetic allergy
• Local sepsis/infection (puncture site or within psoas compartment)
• Coagulopathy
○ Relative contraindications:
• Systemic sepsis (particularly for catheter placement)
• Fixed cardiac output (due to the risk of epidural/subarachnoid spread)
What complications of regional anaesthesia are pertinent to lumbar plexus blockade? (5 marks)
From needle:
• Direct trauma to nerves of the lumbar plexus/intraneural injection
• Dural puncture
• Trauma to retroperitoneal structures/abdominal viscera (e.g. kidney, ureteric injury)
• Retroperitoneal haematoma
• Psoas abscess
From incorrect placement of local anaesthetic:
• Epidural/intrathecal spread of local anaesthetic
From local anaesthetic:
• Hypotension
• Intravascular injection/local anaesthetic systemic toxicity (psoas compartment is highly vascular and muscle tissue demonstrates rapid drug absorption)
Describe the neurovascular supply of the oesophagus (9 marks)
Nerve supply:
• Motor: CN 10*, recurrent laryngeal branches for upper third and vagal plexi for rest
• Sensory: pain fibres run with both parasympathetic (CN 10) and sympathetic fibres** (T2–6, from the middle and lower cervical ganglia)
• Secretomotor: CN 10
Arterial supply:
• Cervical portion: oesophageal branches of inferior thyroid artery (arise from the thyrocervical trunk– third branch of the first part of the subclavian artery***)
• Thoracic portion: oesophageal branches of thoracic aorta
• Abdominal portion: oesophageal branches of left gastric artery (from the celiac trunk)
Venous drainage via oesophageal veins to:
• Cervical portion: inferior thyroid vein (draining to brachiocephalic vein; systemic)
• Thoracic portion: azygos vein (draining to SVC; systemic)
• Abdominal portion: oesophageal tributaries of left gastric vein (draining to portal vein)
Vagal fibres from the nucleus ambiguus supply upper third striated muscle of the oesophagus, fibres from dorsal motor nucleus for lower visceral muscle
**This explains the referred pain of oesophagitis– retrosternal dermatomes T2–6
**In 25%, arises directly from the third part of the subclavian artery
List the relations of the thoracic oesophagus (4 marks)
○ Anterior: trachea, left main bronchus, pericardium/left atrium, (left) recurrent laryngeal nerve, anterior vagal trunk
○ Posterior: vertebral bodies, thoracic duct (crossing to the left at T5), descending thoracic aorta, connections to (accessory)/hemiazygos vein, posterior vagal trunk
○ Right: pleura, azygos vein**
○ Left: pleura, arch of aorta**, thoracic duct (above T5)
**The blue arch is right, the red arch is left
What anaesthetic monitoring devices are placed in the oesophagus and what do they measure? (3 marks)
○ Oesophageal Doppler (cardiac output)
○ Transoesophageal echocardiography probe (cardiac structure and function, fluid filling)
○ Oesophageal temperature probe (core temperature)
○ Oesophageal contractility (depth of anaesthesia)
Whatfeatures,ofthe distaloesophagus and surrounding structures, form the ‘physiological sphincter’ of the lower oesophagus to reduce reflux of gastric contents? (4 marks)
○ Tonic contraction of circular smooth muscle in the lower oesophagus
○ Fibres of the right crus of the diaphragm surround the lower oesophagus
○ Longitudinal folds of oesophageal mucosa occluding the central lumen
○ The oesophagus enters the stomach at an acute angle
○ The terminal 2–3 cm of the oesophagus are below the diaphragm (raised intraabdominal pressure compresses the oesophagus causing a flap-valve effect)
N.B. Gravity is also a contributing factor when upright– hence why patients may experience gastro-oesophageal reflux disease predominantly when lying down
Describe the anatomy of the pituitary gland and its relations (8 marks)
○ An endocrine gland at the base of the brain, composed of a (larger) anterior lobe an (smaller) posterior lobe, separated by a pars intermedia
○ Located in the pituitary fossa (or sella turcica – the ‘Turkish saddle’), a depression in the
sphenoid bone and the central portion of the middle cranial fossa
○ The roof of the sella turcica is formed by a fold dura (the diaphragma sellae); a small perforation allows the pituitary stalk to pass through in continuity with the
hypothalamus (above) and posterior pituitary (below)
Relations:
○ Lateral: cavernous sinus, containing the internal carotid artery and CN 6 (with
CN 3, CN 4, CN 5.1 and 5.2 lying in the lateral wall of the cavernous sinus)
Superior: optic chiasma (anteriorly), hypothalamus and, above that, the third
ventricle
○ Anterior/inferior: sphenoidal air sinus
Posterior: midbrain and pons
What is the hypothalamo-hypophyseal portal venous system? (2 marks)
○ Microcirculation connecting the hypothalamus with the pituitary to expedite transport and exchange of hormones between the hypothalamus and anterior pituitary
○ Blood from the superior hypophyseal (pituitary) arteries supplies the hypothalamus where they form a primary capillary plexus receiving the hypothalamic hormones
○ Blood then drains (by hypophyseal portal veins) to a secondary plexus in the anterior pituitary, where the hypothalamic hormones affect their target cells (in the anteriorpituitary)
○ These capillaries are highly permeable to facilitate the exchange of these hormones
What feature a of acromegaly are relevant to the conduct of general anaesthesia?(5marks)
Airway:
° Up to 70% have obstructive sleep apnoea (OSA) due to generalised hypertrophy/
oedema of upper airway mucosa
° This, combined with development of macrognathia and macroglossia can make bag-mask ventilation and intubation more difficult
○ Respiratory:
° Proximal muscle weakness and potential OSA increase risk of postoperative
respiratory failure
○ Cardiac:
° Hypertension and left ventricular hypertrophy (LVH) lead to increased risk of cardiac ischaemia and failure
○ Endocrine:
° Multiple endocrine abnormalities can occur, in particular diabetes mellitus, hyper-/hypothyroidism and adrenal insufficiency
○ Other:
° Venous cannulation may be difficult due to excess soft tissue
What is the transsphenoidal approach to the pituitary gland? Name the main advantages and complications (5 marks)
Transsphenoidal approach:
○ Elevate the mucosa from the posterior nasal septum (requires fracture/removal
of the anterior bony septum, the posterior part is removed but preserved for closure)
○ Through this opening enter the sphenoidal air sinus and, from here, enter the pituitary fossa
Complications:
°Haemorrhage
°Cranial nerve injury (in particular visual deficit)
°Persistent CSF leak
°Hormonal (panhypopituitarism or transient DI)
°Ischaemic stroke (due to vasospasm)
What are the indications for a popliteal fossa block? (3 marks)
Surgical procedures below the knee:
Foot/ankle surgery (corrective, debridement/amputation, Achilles tendon repair)
Interventional radiology to revascularise lower limb below the knee
Other: sural nerve biopsy, short saphenous vein (SSV) stripping
(Rescue) analgesia for leg/ankle/foot pain (e.g. trauma or postoperative)
Describe the anatomy of the popliteal fossa (5 marks)
Boundaries:
°Superomedial: the ‘semi’ muscles (semimembranosus and semitendinosus)
°Superolateral: medial border of biceps femoris
°Inferomedial: gastrocnemius (medial head)
°Inferolateral: gastrocnemius (lateral head)
°Roof: fascia lata
°Floor (proximal to distal): popliteal surface of femur, capsule of knee joint, popliteus
Contents (superficial to deep):
°Short saphenous vein (pierces roof of popliteal fossa and drains into popliteal vein)
°Tibial and common peroneal nerves*
°Popliteal vein
°Popliteal artery
°Popliteal lymph nodes and fat pack the rest of the fossa
*The terminal branches of the sciatic nerve – the bifurcation is typically at the apex of the
popliteal fossa, but it can occur as far4 proximally as the gluteal region
Describe the cutaneous innervation of the sciatic nerve below the knee (6 marks)
Tibial (L4–S3):
°Lower half of lateral calf and lateral border of foot, including little toe (sural nerve)
°Plantar surface of foot (medial and lateral plantar nerves)
°Heel (medial calcaneal branches)
Common peroneal/fibular (L4–S2):
°Upper half of lateral calf (lateral cutaneous nerve of calf )
°Lower anterolateral calf and dorsum of foot (superficial peroneal nerve)
°First web space (deep peroneal nerve)
(N.B. Also contributes to the sural nerve via a communicating branch)
Describe the cutaneous innervation of the sciatic nerve below the knee (6 marks)
Tibial (L4–S3):
• Lower half of lateral calf and lateral border of foot, including little toe (sural nerve)
• Plantar surface of foot (medial and lateral plantar nerves)
• Heel (medial calcaneal branches)
Common peroneal/fibular (L4–S2):
• Upper half of lateral calf (lateral cutaneous nerve of calf )
• Lower anterolateral calf and dorsum of foot (superficial peroneal nerve)
• First web space (deep peroneal nerve)
(N.B. Also contributes to the sural nerve via a communicating branch)
Describe a technique for performing a popliteal fossa block (6 marks)
Consent
Stop before you block: confirm side and site**
SLIMRAG:
°Sterile procedure (wash hands, sterile gloves, sterile dressing pack)
°Light source/ultrasound
°IV access
°Monitoring (AAGBI minimum standard) °Resuscitation drugs/equipment available
°Assistant (who is happy to assist with regional or general anaesthetic)
°General anaesthetic: ensure equipment/drugs available to convert if required
°Position: supine (flex knee to 30°) or lateral (block limb uppermost), occasionally prone
● Locate skin crease at popliteal fossa and
clean skin of distal lateral thigh with 0.5%
chlorhexidine (allow to dry)
● High-frequency linear array ultrasound probe with sterile cover and gel to identify
sciatic nerve bifurcation (typically 5–10 cm proximal to the popliteal skin crease)
● In-plane technique, 80–100 mm short bevel regional block needle
● Apply local anaesthetic to skin then insert from lateral side (anterior to tendon of biceps femoris)
● After negative aspiration, slowly inject 15–20 ml of local anaesthetic, aiming for
perineurial deposition of local anaesthetic around the division of the sciatic nerve,
confirming negative aspiration after every 5-ml injection
**Particularly important as the patient is often turned either lateral or prone to perform theblock, increasing risk of wrong site block
Block tips…
A peripheral nerve stimulator may be used to guide nerve localisation; however, the sciatic nerve contains sensory nerve fibres at this level – this may lead to false negative results if relying on eliciting a motor response
The popliteal vein is easily compressed by pressure from the ultrasound transducer, andcare must be taken to ensure that the vein has not been cannulated – this is achieved byvisualising the needle tip, negative aspiration, 5-ml aliquots of local anaesthetic, visualisation of local anaesthetic spread and monitoring the patient for signs of local anaesthetic toxicity
Briefly describe the anatomy of the trachea (6 marks)
° Begins as a continuation of the larynx below the cricoid cartilage (C6 level)
> 10–12 cm in length (half cervical, half thoracic), 2.5 cm diameter
°Terminates at the plane of the sternal angle (T4/5 IV disc) at mid-inspiration (but varies with phase of respiration – more inferior in inspiration and superior in expiration)
°Structure maintained by 15–20 C-shaped rings of hyaline cartilage, joined by fibro-elastic tissue
° Posteriorly, trachealis (smooth muscle) joins the ends of the cartilages
° Lined by pseudostratified, columnar epithelium (containing goblet cells)
° Blood supply/venous drainage: inferior thyroid artery and bronchial arteries, drains to inferior thyroid veins
°Nerve supply: recurrent branches of vagus nerve supply mucosa (including pain fibres), upper ganglia of sympathetic trunks supply smooth muscle and blood vessels (vasomotor)
List relations of the trachea in the neck (C6) and thorax (T4) (8 marks)
Neck:
°Anteriorly: anterior jugular veins, sternohyoid, sternothyroid, isthmus of thyroid gland (overlying second–fourth tracheal cartilages), inferior thyroid veins, thyroid ima artery
°Laterally: lobes of the thyroid gland, carotid sheath (common carotid artery, internal jugular vein, vagus nerve)
Posteriorly: oesophagus, recurrent laryngeal nerves (in tracheo-oesophageal grove)
Thorax:
°Anteriorly: left brachycephalic vein, brachiocephalic trunk, left common carotid
artery, arch of aorta, thymus
°Left: arch of aorta (‘red arch’), left common carotid artery, left subclavian artery, left recurrent laryngeal nerve, pleura
°Right: azygos vein (‘blue arch’), right CN 10, pleura
°Posteriorly: oesophagus, left recurrent laryngeal nerve
List immediate/early and late complications of a tracheostomy placed between the second and third tracheal rings (6 marks)
Immediate/early:
- From instrumentation: bleeding, tracheal cartilage fracture, posterior tracheal wall/ oesophageal injury, pneumothorax, laryngeal nerve damage
- From loss of airway: hypoxia, false passage, surgical emphysema
Late:
- From instrumentation: bleeding, infection
- From loss of airway: hypoxia, displacement, blockage
- From scarring: tracheal stenosis, tracheo-oesophageal fistula, trachea granuloma, vocal changes, persistent stoma, dysphagia, disfiguring scar, tracheomalacia
Name the nerves labelled A–E. Describe their area of cutaneous innervation (10 marks)
A) Tibial*
°Lies posterior to the medial malleolus, typically posterior to the posterior tibial artery**
°Gives medial calcaneal branches, which pierce flexor retinaculum to supply the skin of the heel (including weight-bearing surface)
°Divides into the medial and lateral plantar nerves in the foot (under flexor
retinaculum), which provide cutaneous innervation to the sole of the foot
(medial 3½ toes and lateral 1½ toes respectively)***
Also supplies skin over distal phalanges
B) Saphenous
°Largest sensory branch of the femoral nerve
°Below the knee it travels with the great/long saphenous vein
°Sensation to medial calf and medial aspect of the ankle/foot (as far as first MTPJ –‘bunion area’)
C) Sural
°Formed by the union of branches of the tibial and common peroneal nerves
°Below the knee it travels with the small/short saphenous vein
•Passes posterior to the lateral malleolus (cf. saphenous nerve and GSV lie anterior to the medial malleolus)
° Innervation to the lateral aspect of the calf, ankle and foot (including little toe)
D) Deep peroneal/fibular
°Common peroneal divides into superficial and deep branches within peroneus longus
°Deep nerve provides sensory supply to 1st web space
E) Superficial peroneal/fibular
Pierces deep fascia in the distal third (between middle and distal thirds) of the leg (emerges between extensor digitorum longus and peroneus brevis)
°Sensation to lower half of anterolateral leg and ankle, dorsum of the foot via medial and lateral branches
There is no posterior tibial nerve! (This terminology has been replaced, it is now simply the tibial nerve, but is still seen in clinical texts)
**Mnemonic for the structures behind the medial malleolus (from anterior to posterior):
‘Tom, Dick And Very Naughty Harry’
Tibialis posterior, FDL, posterior tibial Artery and Vein, tibial Nerve, FHL
**Aide-memoire for distribution of plantar nerves: medial plantar (like median nerve on
palm of the hand), lateral plantar (like ulnar nerve)
b) Identify structures F–I (4 marks
F) Achilles tendon
G) Dorsalis pedis artery
H) (Inferior) extensor retinaculum
I) Small/short saphenous vein
Which of these nerves lie superficial to deep fascia at the level blocked? (3 marks)
○ Saphenous
○ Superficial peroneal/
○ fibular
○ Sural
(Ankle block)
From time of injection to onset of block, which of these nerves classically takes the longest and why? Why is it the only nerve for which a nerve stimulator would be useful? (3 marks)
○ Tibial takes the longest as it is the largest nerve
○ It is the only nerve in this block with a motor component (saphenous, deep peroneal/fibular, superficial peroneal/fibular and sural are sensory branches at this level)
From the image, name structures 1–5 and the nerves that pass through them (10 marks)
1) Cribriform plate of ethmoid bone (CN 1)
2) Optic canal (CN 2)
3) Foramen rotundum (CN 5.2/maxillary division)
4) Foramen ovale (CN 5.3/mandibular division, lesser petrosal nerve from CN 9)
5) Internal auditory/acoustic meatus (CN 7 including nervus intermedius, CN 8)
Name the landmarks labelled A–C and the venous sinus associated with them (3 marks)
A) Groove for transverse sinus (transverse venous sinus)
B) Groove for sigmoid sinus (sigmoid venous sinus)
C) Internal occipital protuberance (confluence of sinuses)
Ontheimage, demonstrate the boundaries of the anterior, middle and posterior cranial fossae. Describe the principal part and function of the brain associated with each (3 marks)
○ Anterior cranial fossa (frontal lobe): emotion/personality/behaviour, primary motorcortex
○ Middle cranial fossa (temporal lobe): auditory processing, memory and language
○ Posterior cranial fossa (cerebellum): coordinates and regulates voluntary movement (integrates sensory input from spinal cord to motor control for coordination and precision)
What is the name of the region indicated by D? What clinical condition is associated with trauma in this territory and why? What are the clinical features? (4 marks)
○ Pterion – a region on the lateral side of the skull where the plate of bone is thin (see surface marking on illustration)
○ Trauma here is associated with extradural haematoma because the anterior division of
the middle meningeal artery lies on the deep surface, which can be damaged if the overlying bone is fractured
Clinical features:
• Initial lucid interval after trauma
• Subsequent rising ICP with headache, vomiting, confusion, deteriorating consciousness and seizures
CN 3 palsy (ipsilateral dilated pupil in ‘down and out’ position)*
• Contralateral homonymous hemianopia
• Contralateral hemiparesis/brisk reflexes and subsequent features of brain herniation
*CN 3 palsy begins with a dilated (‘blown’) pupil and then adopts the ‘down and out’ position –
the parasympathetic nerve fibres travel on the outside of the nerve and so are affected first by compression on the tentorium cerebelli, before the motor fibres are then compromised
Identify structures A–E in these cadaveric images (5 marks)
A) Axillary artery
B) Radial artery
C) Brachial artery
D) Deep palmar arch
E) Superficial palmar arc
Name the artery running with the following nerve (3 marks):
Radial nerve (in the proximal arm)
Median nerve (in the cubital fossa)
Ulnar nerve (at the wrist)
Radial nerve in the proximal arm: profunda brachii artery
Median nerve in the cubital fossa: brachial artery
Ulnar nerve at the wrist: ulnar artery
Describe collateral arterial supply of hand (8 marks)
○ Supplied from radial and ulnar arteries (arise from the brachial artery at the level of the neck of the radius, in the cubital fossa)
○ They enter the hand to form two arterial arches: superficial (principally from the ulnar) and deep (principally from the radial)
Radial artery:
○ Palpable at the wrist, then continues through the anatomical snuff box as the ‘deep branch’ to form the deep palmar arch (which is completed by the deep branch of the ulnar artery)
○ Gives a superficial branch 2 cm proximal to the wrist crease (passes over the flexor retinaculum, through the thenar muscles and contributes to the superficial arch)
Ulnar artery:
○ Palpable at the wrist, then continues over the flexor retinaculum (in canal of Guyon) to form the superficial palmar arch (completed by the superficial branch of the
radial artery)
○ Gives a deep branch (through the hypothenar muscles), which contributes to the deep arch
Palmar arches:
○ Superficial: supplies medial 3½ digits via palmar digital arteries (cf. opposite to the ulnar nerve distribution, which provides sensory supply to the medial 1½ digits)
○ Deep: supplies the lateral 1½ digits via princeps policis and radialis indicis arteries (cf. median nerve provides sensory supply to the lateral 3½ digits)
○ The two arches are also linked by metacarpal arteries
What is Allen’s test? (4 marks)
Used before attempting cannulation of the radial artery
Test to assess adequate ulnar collateral supply to the hand
Compress radial and ulnar arteries at the wrist
Elevate hand and make a fist for 30 seconds
When opening the hand and the hand is pale (due to limited arterial supply)
Release the ulnar artery: colour should return to the hand within 10 seconds
Poor ulnar arterial supply is indicated if this is prolonged
(The accuracy of this test is questioned)
Name structures A–E on this image of the brachial plexus (5 marks)
A) C6 nerve root
B) Superior trunk
C) Lateral cord
D) Lateral pectoral nerve
E) Medial cutaneous nerve of the arm
Name the nerve roots that contribute to the nerves labelled F–I (4 marks)
F) Ulnar nerve: C8–T1 (sometimes C7)
G) Radial nerve: C5–T1
H) Median nerve: C5–T1
I) Axillary nerve: C5–6
What motor response is demonstrated on stimulation of the lateral, posterior and medial cords of the brachial plexus? (3 marks)
Posterior cord: wrist/finger extension
Medial cord: thumb adduction, wrist flexion
Lateral cord: elbow flexion, forearm supination
Name the part(s) of the brachial plexus targeted by the following blocks (4 marks):
interscalene supraclavicular infraclavicular axillary
Interscalene: roots
Supraclavicular: distal trunks/proximal divisions
Infraclavicular: cords
Axillary: branches (peripheral nerves)
What are the benefits of ultrasound-guided (over anatomical landmark or nerve stimulator) brachial plexus
blocks? (4 marks)
Allows continuous visualisation of needle tip/placement and local anaesthetic spread
Quicker procedure
Faster onset
Longer duration
Higher success rate
Reduced local anaesthetic volume used
Avoidance of discomfort of nerve stimulation (especially if supplying an injury/
fractured limb)
Allows for anatomical variation and differing needle approach
Reduced incidence of intravascular injection
Reduced incidence of pneumothorax
(No difference in incidence of nerve injury demonstrated in current evidence)
On the image, name structures A–E (5 marks)
A) Vertebral artery
B) Basilar artery
C) Posterior communicating artery
D) Anterior cerebral artery
E) Internal carotid artery
What is the origin of A and E? (2 marks)
A) Subclavian artery (first branch of the first part)
E) Common carotid artery (level with the superior border of thyroid cartilage – at C4)*
*Note that the common carotid artery arises from the brachiocephalic trunk on the right, and
directly from the arch of the aorta on the left
Where are the common locations of intracranial vascular aneurysms and with what frequencies do they occur? (6 marks)
Anterior communicating (40%)
Posterior communicating (30%)
Middle cerebral artery (20%)
What is the significance of the circle of Willis? (1 mark)
Provides collateral circulation for the brain, compensating for reduced flow through
individual segments of the arterial circle and thus maintaining blood supply to
the brain
Describe the speech deficit that occurs from occlusion of the:
i) dominant hemisphere middle cerebral artery anterior branch
ii) dominant hemisphere middle cerebral artery posterior branch
iii) dominant hemisphere middle cerebral artery (3 marks)
i) expressive dysphasia (anterior speech area of Broca)
ii) receptive dysphasia (posterior speech area of Wernicke)
iii) global aphasia
Which artery has been affected in a patient suffering from an occlusive stroke presenting with:
i) 6 motor/sensory deficit of the contralateral lower limb
ii) contralateral homonymous hemianopia with macular sparing
iii) motor/sensory deficit of the contralateral upper limb and face (3 marks)
i) ACA
ii) PCA**
iii) MCA
Name the nerve labelled A on the image (1 mark)
CN 10 (vagus nerve)
From which nuclei does it arise? Structure A (4 marks)
○ Dorsal nucleus of vagus (parasympathetic: heart, lungs, gut)
○ Nucleus ambiguus (motor: skeletal muscle of palate, larynx, pharynx)
○ Nucleus of tractus solitarius (special sense: taste from epiglottis, cardiorespiratory andvomiting reflexes)
○ Sensory nuclei of trigeminal (general sense: larynx/pharynx, dura of posterior cranial
fossa, ear*)
*CN 10 supply to ear: lower half of outer surface of tympanic membrane, external auditory
meatus and small area behind auricle
What is the name of this foramen (B) in the base of the skull? (1 mark)
Jugular foramen
Which structures pass through it? Foramen b (4 marks)
Anterior compartment:
Inferior petrosal sinus
CN 9
Middle compartment:
CN 10 and 11
Posterior compartment:
Sigmoid sinus (becoming continuous with IJV)