Table 1 Key features of CMT1A and HNPP

Age of onset mainly in first two decades

Painless attacks of numbness, muscular weakness, and atrophy, recurrent and focal

Presenting symptom is difficulty walking or running

Preceded by minor compression on nerve

Distal symmetrical muscle weakness and wasting, legs > arms

Age at onset mostly in the second or third decade

Pes cavus very frequent

Pes cavus found in 4-47% of patients

Sensory symptoms (stocking-glove distribution) usually less prominent, legs > arms

Full recovery in 50% of episodes, usually in days to weeks

Pain more common than previously recognized

Sequelae rarely severe

Large intrafamilial clinical variability

Reflexes absent or depressed

Large clinical variability between patients, even within family

Homogeneous and diffuse MCV and SCV slowing

Increase in distal motor latencies, especially of median and peroneal nerve

CMAP amplitudes reduced, especially distally in the legs

Focal motor slowing at entrapment sites

SNAP amplitudes frequently reduced to absent

MCV normal to slightly reduced in other segments

SCV decreased and SNAP amplitudes often reduced

Abnormal myelination over the whole nerve length

Segmental de-and remyelination

Onion bulbs

Tomacula pathologic hallmark, but not pathognomonic

Decreased density of myelinated nerve fibres

Variable large-fibre loss