Neuropathy Flashcards
F wave in NCS
What is it?
Give powerful nerve stimulation then see how long it takes to travel down the nerve
Most sensitive in GBS
Decreased persistence and increased latency
What is EMG?
Put needle in muscle to record muscle activity
Sensory neuropathy causes
Diabetes
B12/thiamine (inhale NO, blocks B12 metabolism) - if severe, can affect motor nerves and can be permanent
Renal failure
Amyloid
Sjogren’s (ganlionopathy)
Motor neuropathy cases
Rare
Demyelination
Acute motor axonal neuropathy (variation of GBS; motor weakness instead of sensory) - Japanese people
Painful neuropathy causes
Worse getting into bed at night
ETOH/nutritional
Diabetes/impaired glucose control - if you improve BSL, this can be reversed
B6 toxicity
GBS/AIDP
1) onset
2) Clinical features
3) Diagnosis
4) Rx
5) Prognosis
6) NCS
7) Pathogenesis
1) 4 weeks
2)
Ascending numbness + weakness from feet
Proximal + distal weakness (predominant feature)
Weakness is maximum by 2-4 weeks
Lose reflexes over time
+/- Radicular lumbar and neuropathic pain
+/- autonomic dysfunction
Antecedent infection (C jejuni, viruses, vaccines) 1-4 weeks before GBS
3) CSF (raised protein, no cells) NCS - Takes time to become abnormal - Prolonged F wave latency - Prolonged distal latencies/reduced velocity (demyelination) Anti-GM1 (AMAN) Anti-GM2 (CMV) Anti-GD1a (AMAN) Anti-GQ1 (Miller fisher)
FVC <1L = ICU
4)
IVIG or plasma exchange (both effective but plasmaX is more $$$)
No steroids!!!
5) 85% full recovery, 5% severe disability
6) clinical symptoms come first then nerve conduction studies. Clinical symptoms improve first before NCS improve.
7) B cell mediated –> segmental demyelination. Starts at nerve root because of weakest nerve blood barrier –> radiculopathy
GBS variants
Acute motor-sensory axonal neuropathy (AMAN)
MILLER FISHER
Acute motor-sensory axonal neuropathy (AMAN)
- Japanese people
- NCS shows motor block
- C. jejuni
- GM1 and GD1a
Miller Fisher
- Ataxia, opthalmoplegia, areflexia
- Anti-GQ1
AIDP vs CIDP
AIDP
Progresses over 4 weeks
Proximal weakness
CIDP
Progresses over >8 weeks (cut off is >4 weeks)
Proximal and distal weakness
Usually milder than AIDP
CIDP Dx
CSF: raised protein, no cells
NCS: demyelination/conduction block (similar to AIDP/GBS)
CIDP Rx
IVIG or plasmaX +/- steroids +/- steroid sparing agents
Ab positive disease/response to plasmaX: rituximab
What’s hereditary neuropathy with liability to pressure palsy (HNPP)?
Autosomal dominant
Transient and recurrent motor and sensory mononeuropathies, typically carpal tunnel, ulnar groove and fibular head
Mild mild pressure –> palsy can last hours-weeks
Amyloid neuropathy clinical features
Protein disposition
Small fiber painful neuropathy
Autonomic dysfunction e.g. orthostatic hypotension
Diabetic neuropathy clinical features
Length dependent die back
Small fibre loss leading to pain
Weakness is not a predominant feature till late
Others
- Autonomic neuropathy - resting tachycardia, orthostatic hypotension
Management diabetic neuropathy
BSL control
Gastric bypass
Foot care
Pain neuropathy
1) amitryptyline
2) duloxetine and venlafaxine
3) gabapentin and prgabalin
What’s a mononeuropathy? What’s a mononeuritis?
Individual peripheral nerve problem e.g. radial nerve palsy
Typically pressure related - e.g. CT syndrome
Mononeuritis is inflammation/infection of a single nerve
Carpal tunnel risk factors
Female Diabetes Pregnancy Hypothyroidism Haemodialysis Steroid use RA
Infective cause of mononeuritis?
Leprosy
Consider in patients from low/middle income countries with skin lesions, cutaneous sensory loss, thickened nerves to palpation, or focal mononeuropathies
Before DM, leprosy was the #1 cause of neuropathy. Now its #2.
Responsive to abx
Autoimmune causes of mononeuritis?
Vasculitis
Sarcoid
Which CNs have parasympathetic activity?
TV channels!
CN 3 (SBS lol), 7, 9, 10
What does CN3 do?
Oculomotor nerve
Carries parasympathetic fibers –> constrict pupils
Moves eye down and out
Vasculitic neuropathies
1) Pathophysiology and causes
2) Presentation
3) Diagnosis
1)
- Infarct of nerve –> kills axon
- Causes a mononeuritis multiplex (multiple single inflamed nerves)
- Causes: PAN, RA, Sjogren’s
2) Hyperacute presentation
Both small fibers (pain) as well as larger motor and sensory fibers are affected
3) Nerve and muscle biopsy
Sarcoidosis neuropathy
1) Presentation
2) Most common nerve affected
1) Peripheral nerve involvement
- Polyradiculoneuropathy, peripheral neuropathy, mononeuropathy multiplex
2) CN7
When you get bilateral CN7 involvement, always think of sarcoid!
Typical features of peripheral neuropathy
Symmetrical
Progressively ascends up the lower limbs (stocking distribution)
Distal parts are not getting enough nutrients = “die back”, affects longest nerves first (legs)
Majority are axonal > demyelination
