Nerves Flashcards
Left phrenic nerve
neck - course relation scalenus atnerior
scalenus anterior
IJ
L sclav and L CCA cross where arch
percardium
The left phrenic nerve passes inferiorly down the neck to the lateral border of scalenus anterior.
Then it passes medially across the border of scalenus anterior, parallel to the internal jugular vein which lies inferomedially. At this point it is deep to the prevertebral fascia, the transverse cervical artery and the suprascapular artery.
It descends between the left subclavian and the left common carotid arteries, and crosses the left surface of the arch of the aorta.
It then courses along the pericardium, superficial to the left auricle and left ventricle, piercing the diaphragm just to the left of the pericardium.
It carries sensory fibres from the pleura, pericardium and a small part of the peritoneum.
Nerves required for an ankle block
In order to perform an ankle block, five nerves need to be anaesthetised.
They are
The saphenous nerve (the terminal branch of the femoral nerve) and
Four nerves derived from the sciatic nerve:
The tibial
Sural
Superficial peroneal and
Deep peroneal nerves (not common peroneal nerve).
NOT Common peroneal nerve
The following list of myotomes are associated with key movement patters of the lower limb:
Muscle flexion at hip
L1/L2 - Hip flexion
L2/L3/L4 - Hip adduction, quadriceps (knee extension)
L4/L5 - Hip abduction
L5 - Great toe dorsiflexion.
The most important muscles that produce flexion at the hip are:
Iliacus, and
Psoas major.
Collectively they are termed the iliopsoas muscle. The origin of the iliacus muscle is the ilium and the origin of the psoas major muscle is the lumbar vertebrae and sacrum.
They insert into the lesser trochanter of the femur and extend distally. The action of these muscles is to produce flexion and external rotation of the hip. The nerve supply is by branches of the lumbar plexus (L1, 2, 3) femoral nerve (L2, 3, 4) and short direct muscular branches (T12, L1, L2, L3 and L4).
If the eye is up and out - what nerve is damaged - what muscle does in innervate
how can this happen
Course of the CNIV
why prone to injury
Course of CNVI
Wht does it supply
conseq injury
What does the facial nerve do motor POV
Oculomotor CNIII
disruption - what
The superior oblique muscle is supplied by the fourth cranial nerve, the trochlear nerve.
The superior oblique muscle is supplied by the fourth cranial nerve (CNIV), the trochlear nerve. The function of the muscle is to contol downward movement and inward rotation (intorsion) of the eye. Isolated lesions of the trochlear nerve may result from trauma, ischaemia, tumour or a congenital cause.
The trochlear nerve (CNIV) leaves the dorsum of the brainstem to pass anteriorly between the posterior cerebral artery and the superior cerebellar artery. After piercing the dura it runs along the lateral wall of the cavernous sinus to enter the orbit through the superior orbital fissure to innervate the superior oblique. It has a particularly long intracranial course which makes it particularly prone to injury from blunt trauma to the head.
Injury to the nerve will result in an upward deviation of the eye and slight “twisting of the eye” which will make the patient tilt their head to the contralateral side (away form the lesion).
The abducens nerve (CNVI) is incorrect as this supplies the lateral rectus muscle. Interruption of the nerve supply to this muscle results in the loss of abduction of the eye and it becomes medially rotated. The patient will also experience severe diplopia.
The facial nerve is incorrect as the motor component of the facial nerve supplies the muscles of expression.
The oculomotor nerve (CNIII) supplies all the other extraocular muscles, the papillary constrictors and the levator palpebrae muscle. Disruption of CNIII results in the unopposed action of lateral rectus and superior oblique muscles. The affected eye will look “down and out”, the pupil will be dilated from loss of parasympathetic supply and the patient will have ptosis.
The ophthalmic division of the trigeminal nerve is a sensory nerve (the motor components of the trigeminal nerve supply the muscles of mastication, the temporal muscles, and the pterygoids).
Compression of the optic chiasm casues what vis field defic
where do the project to
Compression of the optic chiasma by pituitary tumours predominantly affects the neurones that decussate at this site. These neurones emerge from the nasal half of the retina and convey the temporal half of the visual field, so bitemporal hemianopia is classically found.
The optic nerve is formed by the axons of ganglion cells in the retina.
It leaves the orbit via the optic foramen and projects to the lateral geniculate body in the thalamus. En route, the nasal fibres decussate forming the optic chiasma above the sella turcica. From the lateral geniculate body, the optic radiation projects to the occipital cortex.
Lesions at different sites in this pathway will produce characteristic visual field defects:
Scotoma reflect partial retinal or optic nerve damage
Complete optic nerve injury produces monocular visual loss
Bitemporal hemianopia is seen with pathology at the optic chiasma
Homonymous hemianopia with lesions compromising the optic radiation and
Cortical blindness with occipital cortex pathology.
Nerves of arm
what supinates
what supplys upper arm
what does the ant itnerosseous do
Ulnar nerve - defecit
median nerve
The musculocutaneous nerve (C5-C7 nerve roots) supplies the muscles of the anterior compartment of the arm, namely biceps brachii, brachialis and coracobrachialis. Their principle actions are to flex the upper arm at the shoulder and the elbow. The biceps brachii muscle is involved with supination of the forearm.
The anterior interosseous nerve (C5-T1 nerve roots) arises from the median nerve at the radiohumeral joint line. It has a motor supply to the radial half of flexor digitorum profundus, flexor pollucis longus and pronator quadratus. An isolated palsy will result in difficulty moving index and middle fingers; weakness in flexors of interphalangeal joint of thumb (FPL) and dorsal interphalangeal joints of the index and middle fingers.
The ulna nerve (C8-T1 nerve roots) is the continuation of the medial cord. The motor component innervates the muscles of the hand except the thenar muscles and two lateral lumbricals, flexor carpi ulnaris and medial half of flexor digitorum profundus. The sensory innervation involves the anterior and posterior surfaces of the medial one and half fingers, and the related palm area.
The median nerve (C6-T1 with contribution from C5 nerve roots) is derived from the medial and lateral cords of the brachial plexus. In the arm, the median nerve is closely associated with the brachial artery. It enters the antecubital fossa between the two heads of pronator teres. It is a mixed sensory and motor nerve, the latter supplying the muscles of the thenar eminence and the lateral two lumbricals. The sensory innervation of the median nerve is the skin of lateral 31/2 digits on the palmar aspect. Damage to the median nerve at this level will cause weakness of grip strength, forearm pronation and lateral finger extension. There is also likely to be sensory symptoms and signs in the areas of distribution outlined above.
The superficial radial nerve (C5-T1 nerve roots) is a sensory cutaneous nerve that arises from the radial nerve supplying the skin on the dorsum of the hand.
Gag reflex - sensory + motor innervation
The gag reflex prevents the passage of material into the aerodigestive tract except during swallowing. It comprises elevation of the soft palate and contraction of the pharyngeal muscles in response to stimulation of the posterior pharyngeal wall.
As with all reflexes, the gag reflex has afferent (sensory) and efferent (motor) limbs. The glossopharyngeal nerve forms the afferent limb and the vagus nerve the efferent.
Unilateral stimulation of the pharynx ordinarily elicits a consensual (bilateral) motor response. In unilateral glossopharyngeal nerve damage, there will be no gag reflex elicited on touching the affected side. Unilateral injury to the vagus nerve causes the soft palate to elevate and deviate toward the intact side when either side of the pharynx is stimulated.
If both the glossopharyngeal and vagus nerves are damaged on one side, then stimulation of the normal side elicits a unilateral response with deviation of the soft palate toward that side, whereas touching the damaged side produces no response at all.
Lower border of neonatal Scord
In early fetal life, the spinal cord is as long as the vertebral canal. During development, however, increase in the length of the cord does not keep pace with the growth of the vertebrae.
At birth the tip of the spinal cord has risen from the level of the second coccygeal vertebra to the lower border of the third lumbar vertebr
What carries light touch and proprio
What about lateral ST tract
The dorsal (posterior) columns are ascending pathways that carry information regarding light touch and proprioception.
The lateral spinothalamic tract is an ascending sensory pathway from the periphery to the thalamus. The first order neurones carry information regarding pain, temperature, coarse touch and pressure.
The anterior and posterior spinocerebellar tracts convey proprioceptive and cutaneous sensation from Golgi tendon organs and muscle spindles to the cerebellum for the coordination of movement.
spinal
What does it do for the block
What does pregn do spread
What spec grav does hyperbaric bupiv have
are they safe in Idiopathic IC htn
what is the side affect with regards to coguh
how
Barbotage involves the repeated aspiration and reinjection of cerebrospinal fluid (CSF) into the syringe whilst injecting the hyperbaric local anaesthetic solution, which increases the spread of the block.
Pregnancy increases the spread of the block due to reduced CSF volume and compressed epidural space.
In the United Kingdom hyperbaric bupivacaine 0.5% (in 8% dextrose) which has a specific gravity of 1.026.
Hyperbaric prilocaine 2% is also availabale for spinal anesthesia.
Epidural and subarachnoid blocks may be safely undertaken in patients with idiopathic intracranial hypertension.
Intercostal and abdominal muscle weakness may impair active exhalation and coughing, although tidal volume and inspiratory pressure are maintained by intact diaphragmatic innervation (C3-5).
ICN are what
which is the subcostal
whats pec major innervated by
how are they connected to symp trunk
The intercostal nerves represent the ventral rami of the first 11 thoracic spinal nerves and run along the costal groove on the lower margin of the rib.
The twelfth, being below the 12th rib is subcostal, hence is called the subcostal nerve.
Each intercostal nerve is connected to a ganglion of the sympathetic trunk by rami communicantes to and from which it carries preganglionic and postganglionic fibres which innervate blood vessels, sweat glands, and muscles.
The pectoralis major muscle is innervated by the lateral and medial pectoral nerves.
Facial nerve supplys what
where does it didive
After exiting the stylomastoid foramen, the facial nerve is entirely motor. It gives off the posterior auricular nerve and branches to the posterior belly of digastric and stylohyoid before entering the substance of the parotid gland.
It divides into five major branches within the parotid gland.
From superior to inferior, these are the:
Temporal branch supplying the extrinsic ear muscles, occipitofrontalis and orbicularis oculi
Zygomatic branch supplying orbicularis oculi
Buccal branch supplying buccinator and the lip muscles
Mandibular branch supplying the muscles of the lower lip and chin
Cervical branch supplying platysma.
Though it passes through the parotid, the facial nerve does not innervate this gland. This is the responsibility of the glossopharyngeal nerve.
Interscalene bloc concern with poor resp fxn
what if RLN block
Whats tapia syndrome
how may horners occur
sy
Successful interscalene block (ISB) will produce an ipsilateral phrenic nerve block.
The phrenic nerve is the sole motor supply to the diaphragm, and ipsilateral hemidiaphragmatic paresis occurs in up to 100% of patients receiving ISBs. Usually, phrenic nerve palsy is well tolerated, and is often unnoticed by healthy patients. However, forced vital capacity decreases by approximately 25%, which can produce ventilatory compromise in patients with limited pulmonary reserve, requiring assisted ventilation.
If the recurrent laryngeal nerve is inadvertently blocked, vocal cord palsy occurs with symptoms of hoarseness and possibly acute respiratory insufficiency. This complication is ordinarily of little consequence unless bilateral laryngeal nerve palsy results, which may produce severe laryngeal obstruction.
Cranial nerve X and XII palsy (Tapia’s syndrome), may also occur following ISB. Symptoms include one-sided cord paralysis, aphonia, and the patient’s tongue deviating toward the side of the block.
Horner’s syndrome may occur when the local anaesthetic spreads to the stellate ganglion with its cervical sympathetic nerves. Symptoms include ptosis of the eyelid, miosis, and anhidrosis of the face. However, the existence of Horner’s syndrome may not indicate that the brachial plexus is adequately blocked.
RLN
L comes off
R comes off
Does it innervate all intrisic muscle
Which is damage more often
what does damage to one or both
The left recurrent laryngeal nerve originates from the vagus as it crosses the aortic arch (the right side comes off the vagus as it crosses the subclavian artery) before looping under the aorta.
The recurrent laryngeal nerves provide the motor supply to all of the intrinsic muscles of the larynx except for the cricothyroid.
The left recurrent laryngeal nerve is damaged twice as often as the right due to its intrathoracic course making it more vulnerable.
A neuropraxia to the recurrent laryngeal nerve results in paralysis of the ipsilateral vocal cord, which causes the vocal cord to adduct (lies near the midline). Complete transection of the nerve results in abduction of the vocal cord.
Brachial plexus formed from where
WHat do they exit spinal colum as
between where and where
What do they divide into
Then what do they become
how are they named then - reln what
The brachial plexus is formed from C5, C6, C7, C8, T1 and occasionally from C4 and T2.
upper trunk c5+6
Nerves exit from the spinal column as roots
-lie interscalene groove
between the muscles of scalenus anterior and scalenus medius merge to form three trunks.
These three trunks divide into anterior and posterior divisions. - behind clavicle
These then unite to become three cords (which are named due to their anatomical relationship with the axillary artery).
The brachial plexus is covered in a fibrous sheath from its origin to the axilla.
Trigem neerve
wat does it do
how many division
what do they prvide
where do they emerge
The trigeminal nerve is a mixed nerve providing sensory supply to the face and motor supply to the muscles of mastication, anterior digastric, mylohyoid, tensor tympani and tensor palati.
It has ophthalmic (V1), maxillary (V2) and mandibular (V3) divisions.
The ophthalmic division divides into lacrimal, frontal and nasociliary branches before exiting the skull via the superior orbital fissure.
The maxillary division emerges from the skull through the foramen rotundum, while the mandibular division transits the foramen ovale.
The stylomastoid foramen conveys the facial nerve and the foramen lacerum small meningeal branches of the ascending pharyngeal artery and emissary veins.
CNIII palsy
In surgical third nerve palsy, ptosis and mydriasis are evident and the eye looks ‘down and out’. These features reflect loss of innervation to all the major structures supplied by the oculomotor nerve.
Oculomotor nerve palsy causes ptosis due to paralysis of levator palpebrae superioris. The eye is rotated down and out due to the unopposed actions of the superior oblique and lateral rectus muscles.
Surgical (compressive) causes of a third nerve palsy disrupt the parasympathetic pupillomotor fibres on the periphery of the nerve causing mydriasis.
In contrast, medical (ischaemic) causes of a third nerve palsy leave the superficially located parasympathetic fibres relatively unaffected and the pupil is spared.
Ptosis, anhydrosis and miosis is the classic triad of Horner’s syndrome and reflects loss of sympathetic innervation to the tarsal muscle of the upper lid, facial skin and dilator pupillae, respectively.
Trigeminal neuralgia - px where
Trigeminal neuralgia is neuropathic pain in the distribution of the trigeminal nerve.
Episodes of paroxysmal shooting or sharp natured pain occur typically provoked by stimuli such as light touch, eating, washing, talking or air currents on the face. Patients may describe ‘electric shock-like pain’. Pain is more common in the maxillary (V2) and mandibular (V3) divisions of the trigeminal nerve than the ophthalmic division (V1). It is more frequently seen in patients over 50-years-old and in those with multiple sclerosis but can occur in young adults. It is typically unilateral, although may be bilateral in multiple sclerosis.
The cause is not always known. Many patients are found to have an aberrant vascular loop compressing the nerve on MRI scan. Other potential causes include micro-vascular aneurysms, tumours, arachnoid cysts in the cerebellopontine angle or secondary to traumatic events such as car accidents.
There are no specific investigations to diagnose trigeminal neuralgia. However, clinical assessment of cranial nerve function should be carried out due to the association with multiple sclerosis and also brain tumours. Any abnormalities should prompt cerebral imaging. There is an argument for cerebral imaging in all patients as MRI can be used to detect vascular compression of the trigeminal nerve near the pons. If this is the case micro-vascular decompression of the aberrant vessel provides immediate pain relief in approximately 75% of patients.
Cluster headaches are classically felt as a deep dull aching pain in the retrobulbar, cheek and chin area lasting several hours.
Giant cell arteritis is commonly felt as a continuous pain the forehead, temple and neck area and may be associated with jaw claudication.
Atypical facial pain may occur in any area and be of various characteristics.
The signs and symptoms of disorders of the temporomandibular joint include:
Aching facial pain or in and around the ear
Difficulty chewing or pain whilst chewing
Pain or tenderness of the jaw
Pain in one or both of the temporomandibular joints
Cracking of the joint when opening the mouth
Locking of the joint, making it difficult to open or close your mouth
Post-herpetic neuralgia needs to be excluded and is the persistence of pain in the affected dermatomes, after the resolution of an acute herpes zoster infection (shingles). The diagnosis is usually made if pain persists or arises at least three months after the skin lesions are healed. The commonest areas affected are in the thoracic dermatomes and the ophthalmic division of the trigeminal nerve.
How to block for bunion surgery
An ankle block is a highly effective technique for bunion surgery. The selective block of the superficial peroneal, deep peroneal and posterior tibial nerves would be sufficient for anaesthesia and postoperative analgesia.
Superficial peroneal nerve (L2-S1) is a mixed motor and sensory nerve. It innervates the peroneus longus and brevis muscles and provides the sensory supply to the anterolateral aspect of the leg, the anterior aspect of 1st, 2nd, 3rd and 4th toes (with the exception of the web space between 1st and 2nd toes).
The sensory supply to the web space between 1st and second toes is provided by the deep peroneal nerve (L4-5).
The sensory territory of the saphenous nerve (L3-4) in the foot extends to the proximal part of the midfoot on the medial side.
The sensory supply of the sural nerve (S1-2) innervates the lateral aspect of the little (fifth) toe. The posterior tibial nerve provides sensation to the heel, medial (medial plantar nerve), and lateral (lateral plantar nerve) sole of the foot.
Vagus CnX
emerges where
what does it give off
What suplies cricothyroid muscle
WHat supplies the muscle of the palate
The vagus nerve (tenth cranial nerve) has both sensory and motor divisions.
It emerges from the anterolateral surface of the medulla as a series of 8-10 rootlets in a groove between the olive and the cerebellar peduncle. It passes through the jugular foramen and descends within the carotid sheath between the internal carotid artery and internal jugular vein (common carotid from the upper border of the thyroid cartilage).
The right recurrent laryngeal nerve passes below and behind the subclavian artery and passes upwards behind the common carotid artery. The left recurrent laryngeal nerve passes around the ligamentum arteriosum.
The cricothyroid muscle is supplied by the external laryngeal nerve. The other laryngeal muscles are supplied by the recurrent laryngeal nerve.
All the muscles of the palate are supplied by the cranial part of the accessory nerve via the pharyngeal plexus and the pharyngeal branch of the vagus nerve except tensor veli palatini.
This is supplied by the mandibular branch of the trigeminal nerve.
The following infrahyoid muscles are supplied by the ansa cervicalis:
Sternothyroid
Sternohyoid, and
Omohyoid.
Thyrohyoid is supplied by the hypoglossal nerve.
Central cord syndrome
How does it occur
How does it present
Central cord syndrome: Is the most common incomplete spinal cord lesion. The spinal cord is injured in central grey matter and results in proportionally greater loss of motor function to upper extremities than lower extremities with variable sensory sparing;
The nerve fibres responsible for lower extremity motor and sensory functions are located in the most peripheral part of the cord, whereas fibres controlling the upper extremity and voluntary bowel and bladder function are more centrally located; the sacral tracts are positioned on the periphery of the cord and are usually spared from injury.
This type of injury is associated with cervical spondylosis and extension in the elderly or hyperextension injury in middle age.
How does anterior spinal artery infarction present
Anterior spinal artery infarction: The anterior spinal artery is a single long anastomotic channel that lies at the mouth of the anterior central sulcus and supplies the circulation to the anterior two thirds of the spinal cord. Eight to ten unpaired anterior medullary arteries are branches of the larger afferent aorta and vertebral and iliac arteries. These feed into the anterior spinal arteries.
The largest anterior medullary artery, the great anterior medullary artery of Adamkiewicz, which is susceptible to occlusion with neurologic deficit, is located at the lumbar enlargement, usually at L2 on the left side (but may be at any point from T8 to L2).
Infarction of the anterior spinal artery causes motor paralysis below the level of the lesion due to interruption of the corticospinal tract, and loss of pain and temperature sensation at and below the level of the lesion. Proprioception and vibratory sensation is preserved, as it is in the dorsal side of the spinal cord.
B
Brown sequard
Aortic disease has produced spinal infarction in a variety of situations including dissecting aneurysm; aortic surgery, especially with aortic cross-clamping above the renal artery, atherosclerotic embolisation; aortography; and aortic thrombosis.
Brown-Sequard syndrome is characterised by ipsilateral upper motor neurone paralysis and loss of proprioception, with contralateral loss of pain and temperature sensation. Causes include trauma, neoplasm and multiple sclerosis.
Spinal cord infarctions are rare, especially at the cervical level and in the posterior spinal artery territory. Moreover, this diagnosis is difficult to establish as the clinical picture varies. Even if sensory patterns appear as cardinal signs, their distribution can be very variable.
Cauda equina syndrome:The spinal cord ends at L1 and L2 at which point a bundle of nerves travel downwards through the lumbar and sacral vertebrae (L1-5 and S1-4). Injury to these nerves will cause partial or complete loss of movement and sensation in this distribution.
Small muscle handle innervated by
he small muscles of the hand are innervated principally by T1.
