POLYNEUROPATHY:
1.Nerves are part of peripheral nervous system , so neuropathy will never explain upper motor signs like up going planters etc.
2.Longest nerves are affected first as a rule so poly neuropathy will almost always start from feet & then legs. By the time it reaches close to mid shin it starts involving hands as well. If it has reached to knees or above & upper limb are not affected its not neuropathy rather its either lumber plexopathy or lumber root problem. Similarly if it starts from upper limbs before it has involved feet & shins, it’s most likely cervical radiculopathy. If upper & lower limbs are afafected simultaneously always think of plexopathy, polyradiculopathy or multifocal motor axonopathy rather than neuropathy.
3.Pes cavus or claw toes etc indicate chronic process, so acute causes like GBSyndrome or drug related or vasculitic etc are less likely.indicate long standing causes like hereditary or other chronic causes more than acute.Signs of atrophy like shiny& dry skin or hair loss ( lack of sensory supply) muscle wasting etc also indicate chronicity & rules out acute causes.
- Presence of any upper motor signs like ungoing planters or exaggerated reflexes or will indicate either additional cause to explain these signs or its not neuropathy at all. Neuropathy with UMN signs ( up going planters etc ) is seen in
Neuropathy with cord compression
SCID ( B12)
Neurosyphilis
Friedrich ataxia etc etc
Myeloradiculopathy etc
5.Associated weight loss ,fever,inflammatory symptoms/signs/markers, rash , high ESR etc indicate systemic cause like vasculitis, malignancy etc. Combination of neuropathy with myositis also indicates systemic cause like malignancy or vasculitides. rash may also indicate Porphyria.
6.Mononeuropathy can be a beginning of polyneuropathy if no local cause of mononeuropathy or Mononeurtitis Multiplex is found. so follow up & workup may be needed.
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Diabetes is very common cause of polyneuropathy but it should be long standing diabetes & usually inadequately controlled.If some one has diabetes only for a few years which is well controlled,his /her neuropathy should have some other cause.Untreated Myeloma & malignancies usually don’t have long enough course to cause signs of chronicity. Similarly drugs usually are stopped well before the chronicity phase.Some of the causes will be very obvious if they cause neuropathy like Uremia or hypothyridism will be very florid befor ethey reach the stage of neuropathy. Age related neuropathy is usually not widespread but limited to lower shins only. it doesnt spread to hands or above the midshin.
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Pure motor,pure sensry,or mixed varieties can be seen. Usually metabolic toxins affects motor nerves more ,but dividing the causes on this basis is not always helpful.
9.Workup depends on what we think on clinical ground. nerve conduction is not always needed to establish the diagnosis but can be done in questionable situations. csf analysis & f wave studies are helpful if suspecting radiculopathy ,f wave abnomrlaities usually indicates motor radiculopahy. vasculitic workup, work up for malignancy etc depends upon clinical suspicion. diabetes should always be checked as patient may not be knowing that he/she has diabetes. may not find cause in 20-30% cases but that should not be case with every patient.