Neurology Flashcards
Describe the features that peripheral neuropathy may present with
Symmetrical weakness, more likely to be distal than proximal
Glove or stocking distribution of sensory loss - more distally (this may not be present in HSMN)
Distal areflexia
Can affect multiple sensory modalities
Causes of peripheral neuropathy with a mostly sensory loss
Metabolic - DM, B12/B1/B6 deficiency, uraemia, hypothyroid
Toxins - chemo (vincristine, cisplatin), alcohol, other drugs inc phenytoin/isoniazid
Immune - CIDP, vasculitis
Paraneoplastic
Which bedside tests and investigations would you request for peripheral neuropathy?
CBG, urine dipstick, fundoscopy
FBC, U+Es, LFTs, CRP/ESR, HbA1c, B12, thyroid, Ig and serum elecrophoresis
Nerve conduction studies and needle EMG, nerve biopsy
How do nerve conduction studies work? (Hard)
Involves electrical stimulation of a peripheral nerve and recording the amplitude and deriving the velocity of action potential conduction
Amplitude is normally small for small nerves and large for larger compound muscle action potentials
What might a nerve conduction study show in a demyelinating neuropathy?
In demyelinating neuropathies, the velocity is slowed but the amplitude is preserved
What might a nerve conduction study show in an axonal neuropathy?
In axonal neuropathies, the velocity is preserved but the amplitude is slowed
What is mononeuritis multiplex?
This refers to involvement of multiple separate peripheral nerves, either simultaneously or serially. The pattern of nerve involvement is random, multifocal and often evolves quickly, sometimes progressing to a series of nerve lesions with confluent, symmetrical deficits that mimic a distal symmetrical polyneuropathy.
What is the mechanism of neuropathic pain? (Hard)
Disruption of the normal mechanisms in pain transmission lead to pain even without stimulus - this may be an aberrant response to previous inflammation or arise de novo in nerves
Aberrant mechanisms may include:
- Inflammation sensitising uninjured nerves
- Proliferation of sodium channels leading to hyperexcitability
- Demyelination provoking sensitisation
- Ischaemia or trauma centrally
What are some examples of an acute polyneuropathy?
Guillain Barre syndrome
What are some examples of a chronic demyelinating polyneuropathy?
Most forms of Charcot-Marie-Tooth disease
CIDP
Paraproteinaemic demyelinating polyneuropathy (associated with antibodies to myelin-associated glycoprotein)
How can you differentiate between a cerebellar and sensory ataxia?
You would expect to see nystagmus/ocular involvement/staccato speech in cerebellar ataxia. You may see head tremor or truncal ataxia.
Impaired sensory disturbance in any modality should make you think of sensory ataxia
Causes of cerebellar ataxia
Vascular - cerebellar stroke
Inflammatory - MS, Miller-Fischer
Toxins - alcohol, B12 deficiency, lithium, valproate
Inherited - Spinocerebellar ataxia, Friedreich ataxia
Malignancy
Neurodegenerative - MSA
Infection - enchephalitis, CJD, syphilis
Types of motor neurone disease
Amyotrophic lateral sclerosis (most common)
Progressive muscular atrophy
Primary lateral sclerosis
What signs will you find on examination in MND?
ALS - UMN and LMN mixed signs
PMA - predominantly LMN, but may have UMN later
PLS - predominantly UMNs usually involving the face e.g. corticobulbar dysarthria or pseudobulbar palsy
Diagnosis of MND
Usually a clinical diagnosis, with electrophysiological tests providing supportive evidence
Exclude other causes with neuroimaging
