Second Year Neurology

1. Second Year Neurology Big dogs study group

2. MISC INFORMATION • From C1, continuous with medulla oblongata, to L1/2, ending with conusmedullaris and filumterminale. Expansion in cervical and lumbar areas • Check for Lhermittes, Brudzinski and Kernig’s signs. • Acute areflexic flaccid paralysis – LMNL in the acute stage of “spinal shock” then later leads to UMNL. Usually due to Ischemia or acute trauma. • Injury to the spinal cord may lead to a sensory level whereby there is a LMNL at the level and UMNL below that. • Spinal cord is organised somatotopically – as seen in picture originally. Dorsal Colums : Fasiculusgracilis is more medial and conveys information from lower extremities and trunk and is T6 and below. FasiculusCuneatus conveys upper extremity information and is more lateral in the cord.

3. TERMINOLOGY • Entire nervous system derives from the Ectoderm • Neurapraxia – a temporary paralysis of a nerve caused by ischemia or compression on the nerve. There are little or no sensory deficits and the nerve structure is completely intact, recovery is in hours to weeks • Axonotomy – a more severe nerve damaged normal causes are serve compression/crush injuries and slight stretching of the nerve. There is paralysis and sensory deficits. Disruption to the axon and endoneurium, the epi/perineurium are intact. Degeneration and then regeneration occurs to the axons distal to the site of injury. Prognosis is good but recovery can take many months • Neurotomy – most severe nerve injury, caused by trauma such as stretch, laceration. There would be complete paralysis and loss of sensory information. The nerve, endoneurium, perineurium and epineurium are all disrupted. Degeneration of the nerve occurs and prognosis is poor. Surgical reattachment of nerve may or may not help. • Paralysis – loss or reduction in motor function • Paraesthesia – triggering, numb sensation of the skin • Palsy – complete or partial muscular paralysis often with sensory loss • WALLERIAN DEGENERATION

4. Mononeuropathy – a lesion of a single peripheral nerve e.g. Saturday night palsy effacing the radial nerve only is a mononeuropathy. • Mononeuritis multiplex – inflammation of more than one peripheral nerve in an asymmetrical patten. Affects more than one peripheral nerve and can cause motor and sensory deficits. Can be caused by diabetes melitis, SLE, infections such a HIV, vasculitides and rheumatoid arthritis. Aka Multiple Mononeuropathy. • Polyneuropathy – a lesion of many peripheral nerves normally symmetrical and starts distally. Can be due to infections, cancers, toxin and nutritional defects. Radiculopathy – a lesion affecting a single nerve root. • Polyradiculopathy – a lesion affecting many nerve roots. Dysaesthesia - abnormal unpleasant sensation e.g. burning, wetness, itching, electric shock, pins and needles. • Polyradiculoneuropathy – multiple nerve roots and peripheral nerves e.gguillainbarre or CIDP • Allodynia – Pain from normally non-painful stimulus

5. Peripheral Neuropathy • Peripheral neuropathy • Description – lesion of a peripheral nerve caused by disease or injury • Signs – decreased muscular tone and tendon reflexes, fasciculation's, muscular atrophy and weakness/paralysis and sensory deficits. • Symptoms – weakness, numbness • Underlying causes – compression, stretched nerves, impact trauma, infections, arthritides, diabetes mellitis, infections, diseases. • DCBCDV – drugs, carcinoma, b vitamins, chemicals, drugs, vasculopathy.

6. GuillainBarre • GuillainBarré Syndrome is a condition that evolves rapidly over a few days, commonly after an infection such as Campylobacter enteritis, which is believed to trigger an autoimmune response. The pathology attacks the myelin rather then the axons, so is classed as a demyelinating polyneuropathyand/or polyradiculopathy. Begins with limb weakness and sensory symptoms, worsening day by day for up to a fortnight (occasionally longer). Whist the illness can be self-limiting, it can proceed to cause serious paralysis in the limbs and trunk, and even in cranial muscles. Involvement of autonomic nerves can affect blood pressure, heart rate, and cause serious constipation. Hospitalisation should be compulsory until the process of deterioration has come to an end, since involvement of chest and bulbar muscles can necessitate ventilation and naso gastric tube nutrition. It is possible for aspiration pneumonia to occur, as well as DVT, PE, and cardiac arrhythmia. The patient’s vital capacity should thus be measure twice daily, and intravenous immunoglobulin and plasma exchange can be used to some benefit. Steroids have not been seen to have any effect. Whilst the ultimate prognosis is very good, the progressive loss of function can be very disturbing for the patient. The myelin sheaths will be reconstituted, and a raised CSF protein will be a diagnostic marker.

8. UMN weakness • Results from damage to corticospinal tract between motor cortex and spinal cord. • If lesion is above pyramidal decussation (lower medulla), weakness is contralateral to lesion. If lesion is below decussation, weakness is ipsilateral. • Increased tone/spasticity, egspastic catch in pronators and hand flexors on extension of wrist, clasp-knife phenomenon in extensors of legs, flexors or arms, clonus at ankle after abrupt stretch. • Pyramidal-pattern weakness: patient adopts posture of flexed and pronated arms with clenched fingers, extended and abducted legs, with plantar flexed feet. Caused by preferential sparing of anti-gravity muscles (upper flexors, lower extensors) • There is no muscle wasting or fasciculation. • Tendon reflexes are brisk, and plantar responses are extensor. UMN syndromes • Hemiparesis = a result of unilateral lesion of cerebral hemisphere or brainstem on contralateral side to symptoms. Face involved if lesion is above the pyramidal decussation, spared if lesion is below. Most commonly the result of a stroke. • Tetraparesis = pyramidal weakness of all four limbs, due to lesion in brainstem or high cervical cord. If UMNs are damaged, a ‘spastic’ tetraparesis occurs. Commonly due to cervical spondylosis, MS, trauma, less commonly due to neoplasia, RA at C1/C2 joint, arteriovenous malformations. Brainstem pathology normally associated with cranial nerve symptoms. Weakness of all four limbs can also be caused by motor neurone disease, polio, disorders of NMJ, muscle disease. Myeloradiculopathy = LMN signs in arms and UMN signs in legs, from radiculopathy usually at C6/C7, associated with cervical spondylotic myelopathy. • Paraparesis = usually due to spinal cord disease, so shows signs of a UMN lesion (‘spastic paraparesis’). Commonly caused by MS or extrinsic cervical compression (spondylosis). More rarely caused by cerebral lesion affecting both cortical leg areas in brain eg parasagittal meningioma. ‘Flaccid paraparesis’ can be caused by lesion in caudaequina such as infiltrating neoplasm or central lumbar disc prolapse, leading to mixed UMN and LMN signs. • Monoparesis= isolated upper limb lesion. A stroke in a distal branch of the middle cerebral artery is a common cause, as well as lesions caused by MS, abscesses and granulomas.

10. LMN weakness • Tone of muscle decreases • Fasciculation; brief, flickering contractions. • Pain and sensory disturbance occurs if lesion affects mixed nerve • Tendon reflexes are lost/diminished depending on severity of LMN lesion. Abdominal and cremasteric reflexes are spared. • Weakness and wasting in focal pattern – occurs in groups of muscles if multiple levels of LMNs are affected, pattern depends on site of lesion: • Anterior horn cell disease is caused by motor neuron disease, infections eg poliomyelitis, toxins or structural pathology egsyringomyelia or intrinsic cord tumour. Begins distally, mimicking peripheral nerve lesion, but eventually causes generalised weakness and wasting. • Radiculopathies lead to weakness and wasting in the relevant individualmyotome • Plexopathies produce weakness and wasting in broader range of nerve roots and myotomes. • Neuropathies – mononeuropathieseg carpal tunnel, multiple mononeuropathieseg multiple single nerve involvement from diabetes, sarcoid, leprosy, vasculitic disease, polyneuropathieseg from diabetes, Guillain-Barre, B12 deficiency (symmetrical distal distribution) • Disorders of NMJ, egmyaesthenia gravis, in which extra-ocular muscles are often the first sign, before bulbar and respiratory weakness and proximal muscle weakness. Reflexes preserved, no sensory involvement. Also, Eaton-Lambert syndrome. • Myopathy – usually bilateral and proximal in shoulder and pelvic girdles. Muscle pain and cramps, wasting, dysphagia, ventilatory weakness. No sensory disturbance.

11. Spinal Cord Anterior 2/3 supplied by the anterior spinal artery with the posterior third by the posterior artery. The posterior artery is x2, paired. The three arise from the vertebral artery, or the posterior inferior cerebral artery, they travel the length of the cord and anastamoses with radicular arteries. These are reinforced by vessels such as the ascending cervical, intercostal and lumbar arteries. Watershed areas: Mid thoracic area, can become ischemic on low blood pressure, stenosis of vessels or trauma. Venous: Six longitudinal interconnecting venous channels, anterior and posterior spinal veins that run the length of the cord. There are also anterolateral and posterolateral spinal veins that run next to the attachments of the ventral and dorsal roots. Drain > A/P Radicular veins > Internal Venous Vertebral Plexus > external plexus > ascending lumbar, azygos or hemiazygos veins. Anterior damage – spinothalamic and corticospinal damage!

12. Ascending Tracts Dorsal columns – carries proprioception and discriminative touch. Cells bodies of the 1st order neurone lay in dorsal root ganglia, axons travel into the dorsal horn and then ↑ dorsal columns ipsilaterally. Neurons associated with the lower thoracic area and below travel in the medial part of the columns the fasciculus gracilis and those associated with the upper thorax and upper extremity travel in the more lateral fasciculus cuneatus. The 1st order neurone travel up the dorsal column and synapse with 2nd order neurones within the medulla oblongata with the nuclei gracilis and nuclei cuneatus. The fibres for the 2nd order neurone then decussate in the medulla as the internal acuate fibres and then ascend in the brain stem as the medial lemniscus. The 2nd order neurones terminate in the ventral posterior nucleus of the thalamus with 3rd order neurones which project into the somatosensory cortex. Spinothalamic tract – carries pain, thermal sensation, crude touch and pressure sensation. Cells bodies of the1st order neurone lay in dorsal root ganglia; axons travel into and terminate in the dorsal horn where they synapse with the cell bodies of the 2nd order neurones. Axons of the 2nd order neurone decussate and pass through the ventral white commissure and then travel in the spinothalamic tract. In the brainstem the fibres lay near the medical lemniscus and are known as the spinal lemniscus. Most 2nd order neurones terminate in the ventral posterior nucleus of the thalamus with 3rd order neurones which project into the somatosensory cortex. Corticospinaltract – Deals with control of voluntary, delicate skilled movements. Cells bodies in the cerebral cortex send axons out which pass down the brainstem and in the ventral medulla oblonga and form pyramidal tracts. Within the pyramidal tracts the fibres undergo subtotal decussation. 75-90% of fibres decussate and enter the contralateral lateral corticospinal tract while 10-25% do not decussate and travel in the ventral corticospinal tract (these fibres still decussate but around there termination). The axons in the corticospinal tract terminate in the ventral horn of the gray matter with motor neurones. • Graymatter – 10 laminae • Dorsal horn – afferent fibre enter the spinal cord. Pain, proprioception, heat (SENSORY) • Ventral horn – cells bodes of motor neurons • Lateral horn – in the thoracic and upper lumbar area of the spinal cord, contain preganglionic sympathetic neurones • Substantiagelatinosa – in dorsal horn around laminae I-III, contains collaterals of afferent fibres associated with nociception. • Clarke’s columns –within the dorsal horn lamina VII, receives afferent fibres from muscle spindles, golgi tendons, tactile touch and pressure receptors • Laminae VII – also contains the lateral horn in the thoracic and upper lumbar regions, and preganglionic parasympathetic neurones in the S2-S4 region of the cord • Laminae IX – within the ventral horn contains alpha and gamma motor neurones which control extrafusal and intrafusal muscle fibres respectively

15. Extrinsic/ Intrinsic Lesion • Spondylotic bar – Chronic over years whereby decrease in disc size, osteophytes and calcification occur. Connective tissue and osteophytes compress the cord, or due to venous/arterial obstruction • Disc Protrusion • Primary neoplasm – Neurofibroma (axilla), Glioma • Metastases – Breast, Prostate, Bronchus Intrinsic: Usually anterolateral spinal cord. Can also affect the local spinal nerve and therefore would also show local dermatomal or mytotomal signs for example. • Primary spinal cord gliomas • Syringomyelia – Primary fluid filled cavity within the spinal cord usually affects the ST tract first as they decussate May also cause horners syndrome (Ptosis, Miosis, Anhydrosis, Enopthalmos) due to sympathetic de-nervation. Further LMNL signs as affecting the gray matter. Worse on Valsalva (Increase Pressure). Usually in the csp and may be associated with a Arnold Chiari Malformation. Cape like loss of pain and temperature, weakness, wasting, • Multiple Sclerosis • Cord Haemmorhage

16. Extra-medullary tumours to spinothalamic  As you know, spinal cord pathways are somatotopically organized.  In the spinothalamictract the lowermost segments (sacral, lumbar) are represented by fibres that lie closest to the outer surface of the spinal cord (laterally).  These fibres are most vulnerable to anterolateral extra medullary compression.  The loss of pain and temperature appears here first, and is most complete, in the sacral dermatomes.  As the tumour expands, the sensory loss gradually ascends towards the site of the lesion.  For example, anterolateral extra medullary compression at T1 first affects fibres in the most lateral part of the tract, i.e. the fibres that arose from the dorsal horn cells in the contralateral (decussation) sacral spinal cord.  The lesion at spinal level T1 then moves medially in the tract to involve axons that arose from dorsal horn neurons in the contralateral lumbar, and thoracic dorsal horn.  Thus the pain and temperature deficit is designated as ASCENDING TOWARD THE LESION (which is at  spinal level T1; sacral first, thoracic last).  Of course, the level of pain and temperature impairment DOES NOT reach the level of the lesion (T1).  The lesion (tumour) is found several segments ABOVE the highest level of the pain and temperature deficit.  Thus, in a lesion of the spinothalamic tract at T1, the pain and temperature loss reaches only as high as T3.  No FIBERS in the ALS at spinal level T1 contain information conveyed into the spinal cord from spinal nerves T1 or T2.  Such information will be conveyed in the tract above the lesion (at spinal levels C7 and C8 respectively). 

17. Intra-medullary tumours -  Tumours that start within one half of the spinal cord tend to compress the inner parts of the ALS or spinothalamic tract that contain the fibres that had just crossed over, (i.e. from cells in the opposite dorsal horn at that spinal segment).  Therefore in patients with intramedullary tumours, the pain and temperature loss starts near the level of the tumour (approximately two levels below).  As the tumour grows laterally within the tract, the pain and temperature deficit involves LOWER regions of the body, that is, the pain and temperature loss DESCENDS in relationship to the location of the lesion.  This results in the sparing of the sacral area (sacral sparing) before the sensory loss is complete. Lesions within the centre of the spinal cord damage the pain and temperature fibres as they cross, resulting in a symmetrical loss of pain and temperature, usually with sparing of other sensory modalities.  Syringomyelia, a cystic expansion of the central canal, is a common cause of such a sensory loss.  It occurs most commonly in the cervical spinal cord, and therefore the sensory loss affects the neck and upper extremities in a cape like fashion.  Keep in mind that only the crossing fibres are damaged.  Thus the pain and temperature deficit is limited only to the regions of the body whose pain and temperature information is being carried in the damaged fibers.  Also remember that the crossing fibres are conveying pain and temperature information from several spinal levels lower.    

18. Dorsal Column Damage • Dorsally situated tumours compress the dorsal or posterior column first, and cause paraesthesia (funny sensations), numbness and impairment of 2 point discrimination, vibration and conscious proprioception on the side of the tumour.  Remember, the dorsal columns are somatotopically organized, such that lateral spinal cord compression results in unilateral damage to fibres arising from dorsal root ganglia close to the lesion, whereas central or medial dorsal spinal cord compression tends to damage fibres from dorsal root ganglia relatively far from the lesion site.  For instance, a lesion laterally within the dorsal columns at C2 will damage dorsal column fibres from C2 (close to the lesion site at C2) and below.  In contrast, a lesion medially within the dorsal columns at C2 will damage sacral fibres (far from the lesion site at C2).  •  Damage to the dorsal columns results in loss of 2pt. discrimination, vibration, and proprioception.  Dorsal column lesions may cause a symptom called the "Lhermitte sign."  The patients experience an electric shock like sensation running through the back and limbs upon flexion of the neck.  This is usually associated with lesions in the cervical cord (compression, multiple sclerosis, subacute combined degeneration from B12 deficiency).  Flexing the neck stretches the dorsal part of the cord, thus irritating some of the sick or dying fibres in the fasciculi gracilis and cuneatus conveying pathological signals. 

21. Brainy… • A lesion of the medulla leads to loss of pain and temperature sensation of the face on the side of the lesion and the opposite side of the body. Light touch, vibration, proprioception usually spared in lateral medullary infarction. Lesion affects the ipsilateral spinal trigeminal nucleus and tract. • A pons or midbrain lesion will impair all sensation on the contralateral side of the body, including the face, since all the sensory tracts have crossed by this point. • Brainstem lesions often accompanied by cranial nerve palsies, ipsilateral cerebellar signs, and contralateral hemiparesis. • A lesion of the thalamus affects sensation of all varieties on the opposite side of the body including the face, often with spontaneous pain and dysaesthesia – thalamic pain syndrome. • In lesions of the parietal lobe, sensory functions are preserved, apart from two-point discrimination and proprioception. Astereognosis = not able to recognise objects by touch, agraphaesthesia = unable to recognise figures drawn on hand. Sensory inattention can also occur to stimuli on contralateral side of body.

22. Descending tracts • Upper motor neurons arranged in a homuncular distribution on the primary motor cortex, situated at the posterior margin of the frontal lobe. • UMNs descend to midbrain in cerebral peduncles then cross as pyramidal decussation in anterior pons and medulla. • Some UMNs synapse with motor nuclei of cranial nerves (CNIII, IV, V, VI, VII, X, XI, XII), forming corticobulbar fibres (motor nuclei in brainstem are ‘bulbar nuclei’) • Remaining axons form corticospinal tracts, descending in lateral white matter of cord. • At each spinal level, some corticospinal fibres enter into the anterior horn of the grey matter, and here synapse with lower motor neurons; anterior horn cells or motor neurons. If these cells are damaged, the syndrome is referred to as an anterior horn cell disorder.

23. Brown-Sequardsyndrome  loss of sensation and motor function (paralysis and ataxia) that is caused by the lateral hemisection (cutting) of the spinal cord. Other synonyms arecrossed hemiplegia, hemiparaplegic syndrome, hemiplegia et hemiparaplegiaspinalis and spinal hemiparaplegia. May be caused by a spinal cord tumor, trauma (such as a gunshot wound or puncture wound to the neck or back), ischemia (obstruction of a blood vessel), or infectious or inflammatory diseases such as tuberculosis, or multiple sclerosis. Brown-Séquardsyndrome is an incomplete spinal cord lesion characterized by clinical presentation reflecting hemisection of the spinal cord (cutting the spinal cord in half on one or the other side). It is diagnosed by finding motor (muscle) paralysis on the same side as the lesion and deficits in pain and temperature sensation on the opposite side on physical exam. This is called ipsilateral (on the same side as the spinal cord lesion) hemiplegia and contralateral (on the opposite side) pain and temperature sensation deficits. The loss of sensation on the opposite side of the lesion is because these nerve fibers of the spinothalamic tract cross the spinal cord. In its pure form, it is rarely seen. Incomplete forms are also observed. The most common cause is penetrating trauma such as a gunshot wound or stab wound to the spinal cord. This may be seen most often in the cervical (neck) or thoracic spine. Other causes are tumors, bleeding episodes, tuberculosis, and multiple sclerosis. The presentation can be progressive and incomplete. It can advance from a typical Brown-Séquard syndrome to complete paralysis. It is not always permanent, and progression or resolution depends on the severity of the original spinal cord injury and the underlying pathology that caused it in the first place. Tabesdorsalis. Tabesdorsalis is a slow degeneration of the nerve cells and nerve fibers that carry sensory information to the brain. The degenerating nerves are in the dorsal columns of the spinal cord (the portion closest to the back of the body) and carry information that help maintain a person's sense of position, vibration, and discriminative touch. Tabesdorsalis is caused by demyelination. It is the result of an untreated syphilis infection. Symptoms may not appear for some decades after the initial infection and include: weakness, diminished reflexes, paresthesias including morbid cutaneous sensations having no objective cause, shooting and burning pains (shins), pricking sensations, and formication (a sensation like that produced by small insects crawling over skin), and hypesthesias (abnormally diminished cutaneous, especially tactile, sensory modalities), tabetic gait (locomotor ataxia), progressive degeneration of the joints, loss of coordination, episodes of intense pain and disturbed sensation), personality changes, dementia, deafness, visual impairment, and impaired response to light. The skeletal musculature is hypotonic due to destruction of the sensory limb of the spindle reflex. The deep tendon reflexes are also diminished or absent. For example, the knee jerk or patellar reflex may be lacking, a characteristic finding in tabes known as Westphal's sign.

24. Subacute Combined Degeneration of the Cord (SCDC) iscaused by B12 deficiency, a result of nutritional deficiency, pernicious anaemia, gastrectomy, disease of ileum egCrohn’s. Develops to a peripheral neuropathy, with sensory ataxia due to loss of joint-position sense, and spastic paraparesis. Ankle jerks are usually lost, but plantar responses are extensor. • Early symptoms can also include areflexic damage to peripheral nerves – develops to UMN damage. Loss of control of bladder, extensor plantar responses, mild dementia, optic atrophy. Do not treat with B6!