HNN Week 1 Flashcards
Draw and describe the branchial plexus:
- roots = C5 - T1
- C5 + C6 = superior trunk
- C7 = middle trunk
- C8 + T1 = inferior trunk
- each of the three trunks divide into an anterior and posterior branch
- all posterior branches form posterior cord
- anterior branches of superior and middle trunks form lateral cord
- anterior division of inferior trunk forms medial cord
- lateral cord becomes musculocutaneous nerve
- posterior cord splits and becomes axillary branch and radial branch
- medial cord becomes ulnar nerve
- branch of lateral and medial cords becomes median nerve
Name the 11 relevant branches of the brachial plexus and where they arise from:
- long thoracic nerve = C5 + 6 + 7
- dorsal scapular nerve = C5
- suprascapular nerve = superior trunk
- subclavius nerve = superior trunk
- lateral pectoral nerve = lateral cord
- lower subscapular nerve = posterior cord
- upper subscapular nerve = posterior cord
- thoracodorsal nerve (middle subscapular nerve) = posterior cord
- medial pectoral nerve = medial cord
- medial antibrachial cutaneous nerve = medial cord
- medial cutaneous nerve = medial cord
Describe the anatomy of the root of the neck:
- C8 and T1 spinal roots join after passing either side of the cervical sympathetic ganglion and pass over the superior surface of the first rib
- subclavian artery and vein also pass over the first rib
- the apex of the lung reaches up to the level of the first rib and so a tumour of the apex of the lung can cause nerve compression
- there are three scalene muscles which are responsible for elevating the ribs and tilting the head to the same side
- > anterior scalene = passes between subclavian vein and artery and attaches from transverse processes of C3-C6 to first rib
- > middle scalene and posterior scalene = pass behind the subclavian artery and the middle attaches to the first rib and the posterior attaches to the second rib
How can the thoracic inlet be divided into three compartments?
- anterior compartment: sternum to anterior scalene muscle
- middle compartment: anterior to posterior scalene muscle
- posterior compartment: after the middle scalene muscle onwards
What is the definition of Horner’s syndrome and the classic triad of presenting features?
- due to disruption of sympathetic nerve supply to the eye causing:
1) ptosis - drooping of eyelid
2) miosis - partially constricted pupil
3) anhydrosis - absence of sweating and dryness of the face, usually unilateral
Why does ptosis occur?
lack of sympathetic innervation to the müller muscle which elevates the eyelid
Why does miosis occur?
lack of sympathetic innervation to the pupillae dilator muscle (which normally dilates the pupil) so the pupillae constrictor muscle is unopposed
Why does anhydrosis occur?
due to lack of sympathetic innervation to the sweat glands of the face
What are the causes of Horner’s syndrome?
1) Issue in the brain:
- brainstem demyelination (e.g. MS)
- cerebral infaraction
2) Cervical sympathetic trunk issues
- cord tumour
- syringomyelia = fluid filled cyst that forms in the spinal cord
3) Damage to T1 root
- apical lung tumour
- first rib damage
- brachial plexus trauma
4) Damage to sympathetic chain and carotid artery in neck
- carotid artery accidentally dissected in surgery (as post-ganglionic fibres from the superior cervical ganglion ascend as a plexus around the carotid artery to supply structures in the head like pupillae dilator muscle)
5) Miscellaneous
- congenital
- idiopathic
What is the pathophysiology of Horner’s syndrome:
- due to a lesion at any point along the sympathetic pathway
1) 1st order neuronal fibres descend from the hypothalamus down the brainstem and terminate in the spinal cord at the grey matter in C8-T2 (ciliospinal centre)
2) preganglionic (second order) sympathetic neurons project out into the ganglia of the sympathetic trunkk and ascend to the superior cervical ganglion
3) from the superior cervical ganglion, pre-ganglionic fibres synapse with 3rd order post-ganglionic fibres which continue up towards the head and form a plexus round the carotid artery
What is the anatomical location of the superior cervical ganglion?
- anterior to the bifurcation of the common carotid artery at the level of vertebrae C1-3
What muscle is involved in controlling eyelid elevation?
Levator palpebrae superioris muscle
- has skeletal and smooth parts
- the smooth part is called the müller muscle and receives sympathetic innervation to open the eyelid
- the skeletal part is supplied by cranial nerve 3 (occulomotor)
How can you investigate possible Pancoast tumour?
- X-ray difficult to view the area around the apex of the lung
- may be able to detect a large mass or tumour at the apex of the lung
- CT scan with contrast used to diagnose the cancer
- (MRI has no advantage over CT of examining the mediastinum)
- biopsy may be taken
How can Pancoast tumour be treated?
- if cancerous cause, treat with radiotherapy if tumour has not spread
- surgery is very difficult and should be carried out by a specialist
- > arteries in the area may need to be replaced by plastic tubing to maintain good blood supply to the arm on the affected side
- use of biological/immunotherapies (stimulate body’s immune system to act against cancer cells)
What is a pancoast tumour?
- type of lung tumour found at lung apex
- named after professor who discovered it
- most pancoast tumours are non-small cell carcinomas (NSCC)
- NSCC are 87% of lung cancers
What 3 types of cancer collectively come under the name NSCC?
1) adenocarcinoma
2) squamous cell carcinoma
3) large cell carcinoma
What are the risk factors and aetiology of pancoast tumours?
(same risk factors as for any cancer)
- smoking
- prolonged asbestos exposure
- secondary smoke exposure
- exposure to industrial elements (gold, nickel)
What are the signs and symptoms of a pancoast tumour?
- general cancer symptoms -> weight loss, fever, fatigue, nausea
- severe shoulder pain
- brachial plexus compression
- pain/sensory loss in hand/arm
- compression of recurrent laryngeal nerve = hoarse voice and coughing
- the tumour compresses other structures in the neck and around the thoracic inlet where the first rib surrounds the top of the lung
How do you investigate and diagnose Horner’s syndrome?
- use eyedrops containing small amounts of coccaine in each eye to test pupil reflexes
- carry out imaging to look for tumour (CT best)
What is a dermatome?
- region of skin supplied by a single spinal nerve
What is a myotome?
- group of muscles that a single spinal nerve innervates
How does sensory loss in dermatomes arise?
- damage to the spinal nerve root fibres that innervate that particular area result in numbness
- adjacent dorsal roots innervate overlapping areas of the skin and usually three adjacent dorsal rots have to be damaged in order to achieve complete sensory loss in one dermatome
Describe the dermatomes of the upper limb:
see stripy notebook HNN notes page 1 (posterior of arm is the same)
Draw a spinal cord segment and describe all the main components:
(see stripy notebook HNN p1 notes)
Describe the basic structure of a neuron:
- cell body contains nucleus and dendrites branch off it
- from the cell body an axon extends down which may be covered by a myelin sheath or not
- there are then branches off the bottom of the axon and axon terminals synapse onto other tissues/other dendrites to transmit a signal
What is hemiparesis?
Weakness on one body side
What is aphasia?
When there is SPEECH difficulty - a patient struggles to comprehend or formulate speech due to damage to specific brain regions
What is the motor cortex?
Part of the frontal lobe that gives rise to descending pathways controlling voluntary movement
Name the lobes of the brain:
- frontal
- parietal
- occipital
- temporal
Describe the two main groups of motor tracts:
1) Pyramidal tracts: originate in the CEREBRAL CORTEX and carry motor fibres to the spinal cord and brain stem, are responsible for VOLUNTARY control of face and body muscles
2) Extrapyramidal tracts: originate in BRAINSTEM and carry motor fibres to spinal cord and are responsible for INVOLUNTARY control of body muscles
What is the pyramidal decussation?
At the junction of the medulla and spinal cord, where the pyramidal tract crosses over to the opposite side (this is why one side of the brain controls the opposing side of the body)
What is the corpus callosum?
Broad band of nerve fibres joining the two hemispheres of the brain
How does the medulla oblongata become the spinal cord?
Medulla continues on and the gracile tubercle of the medulla becomes continuous with the spinal cord
How many vertebrae are there and how are they organised?
33 vertebrae:
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral (fused)
- 4 coccyx (fused)
How many spinal nerves are there and how are they organised?
31 nerves:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
- Nerves C1-7 pass ABOVE the corresponding vertebral body
- C8 passes below the body of C7
- the spinal nerves C8 onwards pass through the intervertebral foramen BELOW the appropriate vertebrae
What is the lower limit of the spinal cord?
L1/2 (in children is it L3-4 as their vertebrae grow and get longer leaving the spinal cord behind)
What is the structure of the grey/white matter at cervical level?
average (see stripy notes page 1)
What is the structure of the grey/white matter at thoracic level?
smaller grey matter (see stripy notes page 1)
What is the structure of the grey/white matter at lumbar level?
much larger grey matter (this makes sense as lumbar nerves supply a large area of the body and so a lot of spinal processing occurs) (see stripy notes page 1)
What is the structure of the grey/white matter at sacral level?
(see stripy notes page 1)
What are the parts of grey matter and their function?
- dorsal horn = where sensory information enters
- intermediate horn = contains neurons innervating pelvic and visceral organs
- ventral horn = where motor neurons leave to go and innervate skeletal muscle
What are the parts of white matter and their function?
- dorsal funiculus
- lateral funiculus
- ventral funiculus
What are the meninges?
3 tissue layers that surround and protect the brain and spinal cord
- dura mater
- arachnoid mater
- pia mater
Describe the dura mater:
- outermost layer
- thick and inelastic
- has a periosteal layer and a meningeal layer
Describe the arachnoid mater:
- the middle meningeal layer which is thin and fibrous
- it has trabeculae which bridge the gap between the arachnoid mater and the pia mater across the subarachnoid space
- dura mater and arachnoid mater are separated by subdural space
- contains CSF
Describe the pia mater:
- innermost meningeal layer
- is a UNICELLULAR layer which envelopes the spinal cord
- forms denticulate ligaments which attach laterally to the arachnoid and dura layers for spinal cord stability
- is separated from the spinal cord by the subpial space
What is the difference between the meninges in the brain and in the spinal cord?
- in the brain the periosteal layer of the dura mater fuses with the skull, but in the spinal cord there is the epidural space between the vertebrae and the dura mater
List the layers and spaces of the spinal cord coverings starting with the epidural space:
- epidural space -> between vertebrae and dura mater
- dura mater
- subdural space
- arachnoid mater
- subarachnoid space (containing CSF)
- pia mater (unicellular)
- subpial space
- spinal cord
What is the name of the veins in the epidural space and what is their significance?
Baston veins: they have no valves
What is the conus medullaris and what extends from its end?
- the lowest point of the spinal cord
- filum terminale extends off its end and anchors it stopping the end of the spinal cord from deviating laterally
What is the cauda equina?
The collection of spinal nerves that come off the conus medullaris (looks like horses tail)
What is the arterial supply of the spinal cord?
- anterior spinal artery: travels in the median fissure and is made from branches of vertebral arteries
- two posterior spinal arteries: originate from vertebral arteries and anastomose in the pia mater
Describe the production and what is the composition and function of CSF?
- produced by the choroid plexus = cells in the ventricles of the brain (mainly produced in lateral ventricles but some is made in all ventricles)
- 500ml produced per day and 140ml in subarachnoid space at any one time
- provides mechanical and immunological protection to the brain and spinal cord
- the fluid can be reabsorbed into the venous system of the head
- is a filtrate of plasma and contains many ions like Na, Mg etc. and is slightly more acidic than plasma (pH 7.33 where as plasma is 7.35-7.45)
What is the anatomy of an intervertebral disc?
- nucleus pulposis in the middle -> jelly like material made mainly of water
- annulus fibrosis on the outside -> strong layers of collagen fibres
Describe the different anatomical parts of a vertebrae:
- vertebral body
- pedicles
- transverse processes (come off pedicles)
- superior articular processes (come off pedicles)
- lamina (backwards extensions of pedicles that meet in midline)
- spinous process (formed by lamina meeting)
What is the dermatome map of the lower limb and foot?
see HNN p2 stripy notebook
What is the myotome map of the upper limb and hand?
see HNN p2 stripy notebook
What is the myotome map of the lower limb and foot?
see HNN p2 stripy notebook
What spinal nerves are damaged if knee reflex is lost?
L3/4 (corresponds with myotomes)
What spinal nerves are damaged if ankle reflex is lost?
S1 (corresponds with myotomes)
What is the definition of pain?
An unpleasant sensory AND emotional experience associated with actual/potential tissue damage
How can pain be classified?
- acute or chronic
- cancerous or non-cancerous
- nociceptive or neuropathic
What is neuropathic pain?
- pain due to NERVE damage
What is nociceptive pain?
- pain due to TISSUE damage
What is nociceptive pain and its classifications?
- pain due to TISSUE damage
- > Somatic
- well-localised
- dermatomal
- sharp and constant
- > visceral
- vague distribution
- diffuse spreading to body surface
- dull and cramping
- usually periodic
- can have other symptoms of sweating, nausea and vomiting
What are nociceptors?
- free branching unmyelinated nerve fibres that are activated by any stimuli that has the potential to cause tissue damage
- > mechanical force
- > chemicals
- > extreme temperature
- > O2 deprivation
What chemicals can activate nociceptors?
bradykinin, 5-HT
What chemicals can sensitise nociceptors?
prostaglandins, noradrenaline, ROS