Monday, 12 September 2011

Jagged edge - red flag

Level 1

Red flag: Jagged edge

When you find a glove and/or stocking sensory loss that has a jagged proximal edge you must consider a mononeuritis multiplex; the latter is a cause of a pseudo glove-and-stocking sensory loss.

Length-dependent sensory loss due to metabolic and toxic neuropathies usually have a sharp edge and are in proportion to each other. The following is a rough guide to proportions:

  • Foot and ankles = normal hands and arms
  • Mid calf = hands
  • Knee = mid forearm
  • Thigh = upper forearm or elbow*

* when you get length-dependent sensory loss to the level of the thighs you may find sensory loss in the mid abdomen; i.e. the disease process has started to involve the spinal nerves.

Level 2

A mononeuritis multiplex may only involve the superficial cutaneous nerves leaving the deep nerves intact; if this is the case the tendon jerks will be retained and motor involvement will be minimal.

When a mononeuritis multiplex involves the superficial cutaneous nerves only, please consider cryoglobulinaemia in the differential diagnosis. I assume you know how to take blood and process it to detect the latter; if not find out.

Mononeuritis multiplex due to vasculitis is typically very painful.

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