Neurology Flashcards
What is an axonal neuropathy?
Primary target: axons
Portions of axon distal to site of injury degenerate (Wallerian
degeneration)
Regeneration starts at site of injury and progresses at 1mm per day
Requires intact Schwann cells to guide direction of growth otherwise a traumatic neuroma develops
What is a demyelinating neuropathy?
Primary target: schwann cells
Individual myelin sheaths degenerate, often in a random pattern
New Schwann cells tend to be less functional: slower nerve conduction
What are the different anatomic patterns of neuropathies?
Mononeuropathy: Single nerve affected
Polyneuropathy: Multiple nerves, usually asymmetrical fashion (often ascending)
Mononeuritis multiplex: haphazard distribution of nerves e.g.vasculitis
Polyradiculopathies: nerve root and peripheral nerve damage, diffuse symmetrical symptoms
What is Guillain barre syndrome?
Immune mediated demyelination, usually following infection e.g. Campylobacter jejuni
Rapidly ascending paralysis
Which systemic autoimmune diseases can result in neuropathies?
Rheumatoid Arthritis
SLE
Sjogren syndrome
Name some inflammatory causes of peripheral neuropathy
Guillain-barre
Neuropathy associated with systemic autoimmune disease
Neuropathy associated with vasculitis
What are some infectious causes of neuropathy?
Leprosy
HIV
Lyme Disease
What is leprosy?
Schwann cells become infected with Mycobacterium leprae
Segmental demyelination results
What is Lyme disease?
Bacteria of Borrelia type
Most common sign of expanding area of redness, erythema migrans, begins at site of a tick bite about a week after it has occurred
What are metabolic, hormonal and nutritional causes of peripheral neuropathy?
Diabetes Mellitus: distal symmetrical polyneuropathy, Caused by metabolic and secondary vascular changes
Uraemic neuropathy: distal symmetrical polyneuropathy
Thyroid dysfunction: mononeuropathies, Carpal Tunnel Syndrome
How can malignancy lead to a peripheral neuropathy?
Direct infiltration or compression by neoplasm
Complication of therapy e.g. radiotherapy
Paraneoplastic: Often preceding diagnosis of tumour, Commonly sensorimotor, Secretion of antibodies by tumour
List some types of causes of peripheral neuropathies
Inflammatory Infectious Metabolic, hormonal, nutritious Toxic Malignancy Trauma Inherited
What can cause diseases of the neuromuscular junction?
Antibody mediated
Congenital
Toxin induced e.g. botulism
How do diseases of the neuromuscular junction present?
Painless weakness
Name antibody mediated causes of neuromuscular disorders
Myasthenia Gravis and Lambert Eaton (presynaptic calcium channel blocked)
What is myasthenia gravis?
Autoantibodies directed against AchR on post synaptic membrane
Commonly associated with thymic abnormalities e.g. thymoma
Usual presentation is with ocular problems: Ptosis and Diplopia
Decrementally decreasing skeletal muscle response with repeated stimulation
What can causes skeletal muscle atrophy?
Loss of innervation Disuse Cachexia Old age Primary myopathies
What are the two types of peripheral nerve injury?
Axonal Neuropathy
Demyelinating Neuropathy
What different patterns of atrophy can occur?
Clusters atrophic fibres: neurogenic disease
Perifascicular atrophy: Dermatomyositis
Sparing Type 1 fibres and loss Type 2: Steroid therapy
What does myopathic mean?
Damage to muscle fibres directly
What does neurogenic muscle damage mean?
Disruption of innervation causing secondary changes in skeletal muscle
What investigations might you do to look at myopathies or muscle weaknesses?
Assess for underlying cause: Glucose, FBC for inflammation
Look for evidence of muscle damage: CK, ALT
Look for pattern of change on neurophysiology
Biopsy muscle to see what is happening
What are the three main types of inflammatory myopathies?
Polymyositis
Dermatomyositis
Inclusion body myositis
What is Polymyositis?
Adult onset inflammatory myopathy
PC: myalgia and weakness
Immune mediated: CD8+ T cell
Endomysial mononuclear cell infiltrate
What is Dermatomyositis?
Juvenile or adult onset
Immune mediated damage to small blood vessels: muscle weakness (starts proximal), Skin changes: Heliotrope rash (lilac discolouration), Gottron papules (dusky red patches over knuckles), GI Involvement (Dysphagia), Interstitial lung disease
Perifascicular infiltrates of mononuclear cells
What can cause toxic myopathies?
Prescription medication e.g. Statins
Recreational drugs
Hormonal imbalances e.g. ICU myopathy, thyrotoxic myopathy, hypothyroidism
What are the classes of inherited diseases of skeletal muscle?
Congenital: present in infancy with static or improving changes e.g. Congenital fibre disproportion
Muscular dystrophies: Progressive muscular damage, Defects in ECM around myofobres, Defects in receptors for ECM
What are muscular dystrophies?
Inherited muscle disease, with progressive damage to muscles
Usually manifest before adulthood
What are the different types of muscular dystrophy?
Duchenne and Becker Muscular Dystrophy
Myotonic Dystrophy
Limb-Girdle muscular dystrophies
Fascioscapulohumeral dystrophy
What is Duchenne muscular dystrophy?
Presents before five years
Lack dystrophin
Clinical features: clumsiness, muscle weakness, pseudo- hypertrophy of the calfs (fatty replacement of muscle)
Mortality by 18 is usual
What is Becker muscular dysrophy?
Presents around 11 years
Reduced dystrophin or protein in abbreviated form
Slower progress that DMD
More prevalent
How can diseases of lipid or glycogen metabolism cause muscular dystrophy?
Rhabdomyolisis on excercising or fasting
Slowly progressive muscle loss
• E.g. Acid Maltase deficiency
What are ion channel myopathies?
Mutations in ion channel proteins
AD conditions
Depending on channel affected: Hypertonia or hypotonia
Hypotonia further subclassified on biochemical basis e.g. hyperkalaemia, hypokalaemia
What is a stroke?
Rapidly developing focal neurologic deficit lasting longer than 24h or causing death, which is attributable to a vascular cause
What is lacunar syndrome?
Motor/sensory involvement of >2 - arm, face, leg, ataxic hemiparesis caused by small vessel occlusion
Subcortical or brainstem infarct
What are the immediate management for ischaemic stroke?
Thrombolytic therapy - alteplase
Mechanical thrombectomy
What are early management steps for ischaemic stroke?
Aspirin
Anticoagulants
What long term prevention can be put into place for ischaemic stroke?
Antiplatelet therapy: Dipyridamole, Clopidogrel, Aspirin
Anticoagulant therapy: Warfarin, Newer (Dabigatran, Apixaban, Rivaroxaban, Edoxaban)
Revascularisation: Carotid endoarterectomy, Angioplasty / Stents
Anti-hypertensives
Statins
What is management strategy for a haemorrhagic stroke?
Surgery
How long from an initial stroke do we have to thrombolyse?
4.5 hours
What findings may suggest haemorrhagic stroke and therefore give reason to avoid thrombolysis?
Seizure at onset of stroke
Symptoms suggestive of subarachnoid haemorrhage
Stroke or serious head injury in last 3 months
Major surgery or serious trauma within 2weeks
Previous intracranial haemorrhage
Intracranial neoplasm, AV malformation or aneurysm
GI or urinary tract haemorrhage within 3 months
LP in preceding week
INR>1.7
What is dementia?
Loss of previously acquired intellectual functions in absence of impairment of arousal
What are typical features of dementia?
Memory loss
Visio-spatial functional deficits
Language deficits
Problems with attention and concentration
How does the ICD10 define dementia for the purposes of diagnosis?
For diagnosis, must have evidence of the following:
Decline in memory: learning new information, severe cases recall of previously learned information. Grade mild to severe, present for 6 months
Decline in other cognitive abilities: deterioration in judgement, thinking, planning, organising and processing of information
Decline in emotional control or motivation, change in social behaviour, eg emotional lability; irritability; apathy; coarsening of social behaviour
How does ICD10 classify types of dementia?
Dementia in Alzheimer’s disease
Vascular dementia e.g. multi-infarct, acute onset
Dementia in other diseases classified elsewhere e.g. CJD, Pick’s disease
Unspecified dementia
What tests would be done in a patient presenting with dementia type symptoms to rule out treatable causes?
CT or MRI head
Blood tests: FBC, ESR, U+E, Glucose, Bone profile, LFT, thyroid function tests, B12, Venereal disease research lab test, ANA, ds DNA
Variably: CXR and EEG
Rarely: LP, HIV serology and brain biopsy