Week 1 Flashcards
What are meninges?
Connective tissue surrounding and providing protection to the CNS
Where do C1-7 pass through the intervertebral foramen?
Above their appropriate vertebrae
Where do C8- Coc 1 pass through the intervertebral foramen?
Below their appropriate vertebrae
What is the upper limit of the spinal cord?
Its junction with the medulla oblongata
Where is the lower limit of the spinal cord in a newborn infant?
L3/4 vertebral level
Where is the lower limit of the spinal cord in an adult?
L1/L2 border (as you grow vertebra get bigger??)
What are the alar and basal plates?
Dorsal and ventral aspects of the spinal cord during development, giving rise to the dorsal (alar) and ventral (basal) horns
What are the main features of grey matter?
Dorsal horn, intermediate horn (connects the two horns) and ventral horn
What are the main features of white matter?
Dorsal funiculus, lateral funiculus and ventral funiculus
What is the dorsal for responsible for?
Receiving sensory information from periphery
In which segments ate the dorsal and ventral horns much bigger?
Cervical and lumbar segments, due to innervation of limbs
What is the outer meningeal layer?
The dura mater, a thick inelastic membrane which fuses with the endosteum of cranium at the foramen magnum
What separates the dura and the vertebrae
Epidural space
What is the middle meningeal layer?
Arachnoid mater, a thin, fibrous membrane that bridges the subarachnoid space which contains cerebrospinal fluid
What is the innermost meningeal layer?
Pia mater- a unicellular membrane enveloping the spinal cord which forms 21 denticulate ligaments laterally and is spirited from the spinal cord by the subpial space
What is CSF and where is it made?
A filtrate of blood, made in the choroid plexus within the ventricular system of the brain
How much CSF is produced each day?
500ml, about 140ml of which circulates throughout the subarachnoid space and is reabsorbed into the venous drainage system of the head
What is the purpose of CSF?
Affords mechanical and immunological protection to the brain and spinal cord
What is found in the sub-arachnoid space?
Blood vessels (?) and trabeculae of the arachnoid mater
What plexus of veins exists in the epidural space, and what is its significance?
Vertebral/Batson venous plexus (batson’s veins), major route in spread of cancer form deep pelvic regions due to lack of valves
What is the arterial arrangement in the thoracic section?
2 posterior spinal arteries, anterior spinal artery
What artery supplies the lower 1/3 of the spinal cord, and what is its clinical importance?
Artery of Adamkiewicz, arises from L posterior intercostal artery and is important in anterior spinal artery syndrome leading to loss of urinary and/or decal continence and impaired motor function of legs/spasticity
What is the clinical importance of the lumbar cistern?
Site for epidural injections at L3/4 or L4/5 (supracristal line passes through body of L4) as well as spinal tap (lumbar puncture), allowing withdrawal and measurement of CSF pressure
Where do sensory roots originate?
Dorsal horn?
Where do motor roots originate?
Ventral horn?
What is the purpose of the myelin sheath of A fibres?
Speeding up conduction of electrical impulses
What is the ascending pathway for discriminative touch?
Dorsal column pathway (medial lemniscus pathway)
What is the ascending pathway for pain?
Spinothalamic pathway
What is the descending pathway for voluntary motor functions?
Corticospinal and corticobulbar tracts
What is equilibrium potential?
Membrane potential where number of ions entering the cell equals number of ions leaving the cells
What does the destination of current din an axon depend on?
Axon diameter and number of open pores/channels in membranes
Where can charge travel in axons?
Along axon or out of axon via membrane
What covers axons to increase speed of conduction?
Myelin. Gaps between are called nodes of Ranvier
What are supporting neuronal cells known as?
Glial cells
What does grey matter contain?
Most of the neurone cell bodies and their dendritic processes
What does white matter contain, and why does it appear white?
Axons, and the lipid-rich myelin sheaths around the axons accounts for the white appearance of white matter
What are oligodendrocytes?
Cells responsible for the formation of myelin sheaths in the CNS
What are astrocytes?
Highly branched cells that pack the interstices between the neurones, their processes and oligodendrocytes, providing mechanical support as well as mediating the exchange of metabolites between neurones and the vascular system. Furthermore, astrocytes form part of the blood-brain barrier as well as playing an important part in repair of CNS tissue after damage
What are microglia?
CNS representatives of the monocyte-macrophage system and have defence and immunological functions
What are ependymal cells?
Cells making up a specialised endothelium which lines the ventricles and spinal canal
What is one of the main motor pathways?
Pyramidal tract- this passes form the cortex down through the brainstem, crosses the midline and activates the motoneurons in the spinal cord
What are the 5 types of neurotransmitters?
Cholinergic (ACh), biogenic amines (catecholamines, 5-HT/serotonin), amino acids (glutamate +, GABA -), neuropeptides (endogenous opioids) and miscellaneous (gases: NO, pruines: adenosine, ATP)
What are the sensory receptors from A-alpha fibres?
Proprioceptors of skeletal muscle
What are the sensory receptors from A-beta fibres?
Mechanoreceptors of skin
What are the sensory receptors from A-delta fibres?
Pain, temperature
What are the sensory receptors from C fibres?
Temperature, pain, itch
What basic structures comprise a neuron?
Dendrites, cell body, axon and axon terminal
Describe the medial lemniscal pathway:
Axon (A-beta myelinated fibres) from the periphery projects to the lumbar spinal cord via the dorsal roots. The axon branches into the spinal cord (come back to this), and has an ascending branch which projects into the brainstem, through the dorsal funiculus. The axon then reaches the dorsal column nuclei where it terminates. The second neuron crosses to the opposite side (known as internal arcuate fibres) of the medulla, where it then projects into the thalamus. The third neuron projects from the thalamus to the sensory cortex of the brain via the internal capsule
Describe the spinothalamic pathway:
The primary afferent fibre (A-delta or C axons) projects to the spinal cord, and terminates in the dorsal horn. Primary afferent fibres synapse with the second axon which crosses to the opposite side of the lumbar spine, where it then projects up to the thalamus. The second axon synapses with the third axon which travels to the sensory cortex via the internal capsule
What is the difference between corticospinal and corticobulbar pathways?
Corticospinal from motor cortex to spinal cord, corticobulbar from motor cortex to brainstem for cranial nerves
Describe descending pathways:
Upper motor neuron from motor cortex to brainstem/spinal, lower motor neuron to muscle
What is decussation?
Crossing over of axons from one side of the spinal cord to the other
What is the importance of Brocca’s Area?
Specialised in the motor aspect of speech (speech associated gestures), more commonly in left hemisphere
What is the importance of Wernicke’s Area?
Auditory association cortex- sensory language area, lexical processing, found int he dominant cerebral hemisphere; damage= receptive aphasia
What are the different basal ganglia?
Caudate nucleus, putamen, globus pallidus, thalamus and substantia nigra
What is the function of basal ganglia?
Influence motor activity and control
What structures form the corpus striatum, and what disease affects this area?
Caudate nucleus, putamen and globus pallidus, Huntington’s disease
What area does Parkinson’s disease affect?
Substantia nigra
What is the corpus callosum?
A structure which transmits information between the two cerebral hemispheres
Where is the CSF made?
Choroid plexus of the ventricular system
Where does the 4th ventricle sit?
Between the cerebellum and the bulging pons
What are the four physiological processes involved in nociception?
Transduction, transmission, modulation and perception (conscious)
What is allodynia?
Pain from sources not normally painful (e.g. cotton wool)
What is hyperalgesia?
Abnormally high levels of pain from noxious stimuli
Where does neuropathic pain come from?
Nerve damage
Where does nociceptive pain come from?
Tissue damage
How can nociceptive pain be divided?
Somatic (skin, muscle, bone) and visceral (internal organs)
What are the different sources of lower back pain?
Disc (bulge or rupture), vertebrae (lumbar instability, osteoarthritis), joints (facet, sacro-iliac), muscle (paravertebral, gluteal), ligaments (anterior and posterior longitudinal)
Initially may be a focal physical lesion, but over time, grows to be a multifactorial problem
What type of nerve fibres do the dorsal (white columns contain) in the cervical region?
Large myelinated primary afferent fibres (tactile and proprioceptive)
What major group of neurones have their cell bodies in the lateral horn of the thoracic spinal cord?
Sympathetic preganglionic neurones
What types of sensory information does the superficial dorsal horn process in the lumbar region?
Pain (also temperature or itch)
What types of cells are found in the lateral intermediate grey matter in the sacral region?
Parasympathetic preganglionic neurones
How to motoneurons leave the spinal cord?
Through ventral roots
What do the axons of motoneurons form synapses on and which neurotransmitter do they use?
Skeletal muscle fibres at the neuromuscular junction, using acetylcholine as a transmitter
What are the characteristic features of cervical vertebrae
Foramen transversarium, bifid dorsal spine, small body and large vertebral canal
What are the characteristic features of lumbar vertebrae?
Large body, small vertebral canal, small transverse process without facets, orientation of articular facets
What can superior extension of a Pancoast tumour result in?
Encasement of the C8 nerve root leading to pain in the medial two digits of the hand
What else can encasement of the C8 nerve root by superior extension of a Pancoast tumour cause?
Atrophy of the intrinsic muscles of the hand, particularly the interosseous muscles
What causes pain that radiates down the medial aspect of the arm and forearm to the wrist?
Infiltration of the T1 nerve root by a Pancoast tumour
What are the symptoms of Horner’s syndrome?
Ptosis, miosis, hemifacial/unilateral anhidrosis, loss of head and neck sympathetic tone and enophthalmos
How many neurones are involved in the sympathetic pathway to the eye?
3; first order neuronal fibres arise from the poster-lateral hypothalamus and descend through the brainstem to terminate in the spinal cord at the ciliospinal centre (C8-T2), second-order neuronal fibres exit through the T1 root and travel closer to the lung apex through the paravertebral sympathetic chain and the stellate ganglion terminating in the superior cervical ganglion. Third-order sympathetic fibres exit the ganglion to form a plexus surrounding the internal carotid artery which then ascends into the cavernous sinus, runs a short course on CN VI and then follows the ophthalmic division of CN V to the orbit, supplying the iris dilator muscles and the smooth muscle fibres of upper and lower lid. Vasomotor and sweat glands follow the external carotid artery to supply the ipsilateral side of the face
Where does a Pancoast tumour affect the sympathetic supply to the eye and surrounding structures?
Second-order neuronal fibres passing close to the apex of the lung
How does miosis occur?
Loss of sympathetic drive to the iris dilator muscle resulting in unopposed (parasympathetic) constriction of the pupil
How does partial ptosis occur?
Superior tarsal muscle comprises smooth muscles fibres that aid in the elevation of the upper eyelid when the eye is open and a loss of sympathetic supply results in partial ptosis of upper lid and elevation of lower lid (similar muscle), causing narrowing of the palpebral fissure which causes the illusion of enophthalmos
What is anhidrosis and how does it occur?
The ipsilateral side of the face and neck becoming flushed and dry, most evident on the ear lobes is due to disruption to the sympathetic supply to the sweat glands
How is upper limb swelling and limb discolouration related to presence of a Pancoast tumour?
Tumour compresses the subclavian vein in the anterior compartment of the superior sulcus; loss of sympathetic innervation also leads to loss of vascular tone- oedema results as a failure of venous drainage
How can the thoracic inlet be dived?
Into three compartments, anterior middle and posterior, on the basis of insertion of the anterior and middle scalene muscles on the posterior scalene muscle on the second rib
Describe the anterior compartment of the thoracic inlet
From the sternum to the anterior scalene muscle, it contains the subclavian and internal jugular veins
Describe the middle compartment of the thoracic inlet
From the anterior to the posterior scalene muscle, contains subclavian artery and its branches
Describe the posterior compartment of the thoracic inlet
Beyond the middle scalene muscle, contains branches of the brachial plexus, the sympathetic chain and stellate ganglion
What symptoms are produced by compression of what structure in the anterior compartment of the thoracic inlet?
Discolouration and swelling of the arm produced by occlusion of the subclavian vein
What symptoms are produced by compression of what structure in the posterior compartment of the thoracic inlet?
Ptosis, anhidrosis and miosis are caused by compression of the stellate ganglion, and weakness of the hand is caused by compression or invasion of the brachial plexus
What is a Pancoast tumour?
A malignant neoplasm of the superior sulcus of the lung, with destructive lesions of the thoracic inlet and involvement of the brachial plexus and cervical sympathetic nerve
What clinical features accompany Pancoast tumour?
- Severe shoulder pain, radiating towards the axilla and scapula along the ulnar aspect of the muscles of the hand
- Atrophy of the hand and arm muscles
- Horner’s syndrome
- Compression of the blood vessels with oedema
What type of cancer are most Pancoast tumours?
Squamous cell carcinomas or adenocarcinomas (3-5% are small cell carcinomas)
How are Pancoast tumours diagnosed?
Biopsy and imaging (CT, MRI, PET)
How are Pancoast tumours managed?
- Careful assessment and appropriate staging are performed prior to surgery
- Selective patients are administered preoperative irradiation of 30 Gy over two weeks
- After 2-4 weeks, surgical resection of the chest wall and lower brachial plexus and en bloc lung resection produces a 5 year survival rate of 30%
What are the main mechanical causes of lower back pain?
Trauma, muscular and ligamentous pain, fibrositic nodulosis, postural back pain (sway back), lumbar spondylosis, facet joint syndrome, lumbar disc prolapse, spinal and root canal stenosis and spongylolisthesis
What are the main inflammatory causes of lower back pain?
Infective lesions of the spine and ankylosing spondylitis/sacroiliitis
What are the main metabolic causes of lower back pain?
Osteoporotic spinal fractures, osteomalacia and paget’s disease
What are the main neoplastic causes of lower back pain?
Metastases, multiple myeloma and primary tumour of bone
What does the intervertebral disc consist of?
A soft, gelatinous centre called the nucleus pulposus, which is encircled by a strong, ring-like collar of fibrocartilage called the annulus fibrosus. The structural components of the disc make it capable of absorbing shock and changing shape while allowing movement
What causes a herniated (or slipped) disc?
Nucleus pulposus of IVD being squeezed out of place and herniating through the annulus fibrosis
What cause cause the IVD to become dysfunctional?
Trauma, effects of ageing and degenerative disorders of the spine
In what direction does protrusion of the nucleus pulposus usually occur?
Posteriorly and towards the intervertebral foramen and its contained spinal nerve root
What ligaments support the annulus fibrosis?
Anterior and posterior ligaments
What activities can cause trauma to the IVD?
Lifting in the flexed position, slipping, fallowing on the buttocks or back or suppressing a sneeze
What happens to the gelatinous centre of the disc with ageing?
It dries out, losing much of its elasticity
Which regions of the spine are most often involved in disc herniation?
Cervical and lumbar
Where does herniation usually occur in the lumbar spine?
At the lower levels of the lumbar spine, where the mass being supported and the bending of the vertebral column are greatest
Why is regeneration of nerve fibres in the lumbar spine following disc herniation likely?
Only the nerve fibres of the cauda equina are present- because these elongated dorsal and ventral roots contain endoneurial tubes of connective tissue, regeneration of nerve fibres is likely
What condition is caused by damage to the nerve roots of L4, L5, S1, 2 and 3?
Sciatica, which spreads down the back of the leg over the sole of the foot
What intensifies pain with IVD herniation?
Coughing, sneezing, straining, stooping, standing and jarring motions
What are the most common sensory deficits from spinal nerve root compression?
Parasthesias and numbers, particularly in the leg and foot, though knee and ankle reflexes may also be absent or diminished
What are the signs of disc prolapse between L2 and 3?
- If spinal nerve root L2 is affected, causing sensory changes in the front of the thigh and weakness in hip flexion and adduction
- If spinal nerve root L3 is affected, sensory changes are found at the inner thigh and knee, and weakness in knee extension with reflex loss in the knee
What are the signs of disc prolapse between L3 and 4?
If L4 nerve root is affected sensory changes are found in the inner calf, with reflex loss at the knee and a weakness in knee extension
What are the signs of disc prolapse between L4 and 5?
Weakness with inversion of foot and dorsiflexion of toes and sensory changes in outer calf and upper, inner foot
What are the signs of disc prolapse between L5 and S1?
Reflex loss at ankle, weakness with plantar flexion of foot and sensory changes in the posterior calf and lateral border of foot
What are the features of serious spinal disease?
- Previous history of malignancy
- Younger than 16 or older than 50 with new onset pain
- Unexplained weight loss
- Previous longstanding steroid use
- Recent serious illness
- Recent serious infection
What are the signs of serious spinal disease?
- Saddle anaesthesia
- Reduced anal tone
- Hip or knee weakness
- Generalised neurological deficit
- Progressive spinal deformities
- Urinary retention
What are the symptoms of serious spinal disease?
- Non-mechanical pain -> worst rest
- Thoracic pain
- Fevers/rigors
- General malaise
- Urinary retention
How do you identify serious spinal disease?
- High index of suspicion
- Majority of information in history
- Simple inspection of back with movement
- Simple neurological examination
- Heal/toe walk, squat
What are the features of spinal cord compression?
- Back pain
- Leg weakness
- Limb numbness
- Ataxia
- Urinary retention (with overflow)
- Hyperreflexia
- Extensor plantars
- Clonus
What are the features of cauda equina syndrome?
- Bilateral leg pain
- Back pain
- Urinary retention
- Perianal sensory loss
- Erectile dysfunction
- Reduced anal tone
