Today we discussed peripheral neuropathy. A few points on this very broad topic:
Important differential: 'THIN'
1) Toxic, Metabolic- medications, DM2, EtOH, metals, B12
2) Hereditary- Charcot-Marie-Tooth and variants
3) Inflammatory and infectious- Guillain-Barre, CIDP (chronic inflammatory demyelinating polyneuropathy), vasculitis, and HIV, HTLV, leprosy
4) Neoplastic/paraneoplastic: multiple myeloma
Important points on history:
1) Temporal course- acute (days to weeks), subacute (4-8 weeks), chronic (>8 weeks); relapsing? progressive?
2) Proximal vs. distal motor and sensory symptoms (trouble reaching overhead, climbing stairs vs. opening jars, picking things up)
3) What are the sensory symptoms? negative- e.g. numbness or positive- e.g. paresthesias, burning, throbbing, etc.
4) Questions around above differential
Important physical exam:
Atrophy, fasiculations for LMN lesion
Distribution of weakness- nerve vs. plexus vs. root
Reflexes
Sensory- pin prick, vibration (named nerve vs. nerve root vs. length-dependent)
Important investigations:
FBG, HbA1C
CBC, Cr, Vitamin B12, TSH, serum and urine electrophoresis, HIV
Multiple named nerve palsies = mononeuritis multiplex
Essentially diabetes-related vs. vasculitis.
Common nerves involved in DM2: CN III, IV, VI, median nerve, peroneal nerve.
Vasculitides that commonly cause mononeuritis multiplex: Churg-Strauss, polyarteritis nodosa, rheumatoid arthritis with vasculitic component
Link:
Click here for an excellent review of peripheral neuropathy from Lancet
