Clinical spectrum of the tomaculous neuropathies. Report of 60 cases and review of the literature.

Tomaculous neuropathy has a distinctive pathological pattern of myelin thickenings in a high proportion of internodes but no specific pattern of nerve degeneration. We have analyzed the variable clinical expression of this disorder in a large series of patients. Different phenotypes have been recognized: the majority of our patients (52 cases) had hereditary neuropathy with liability to pressure palsy (HNPP) showing wide variability of clinical progression and of severity of the single episodes. 3 patients suffered from familial recurrent brachial plexus neuropathy (FBPN); 5 patients had a symmetrical progressive sensorimotor involvement of the limbs (SSMN), predominantly in the distal portions and leading to permanent disability. The explanation for this clinical variability does not emerge from our data or from the literature. Segmental demyelination is the major change correlating with the episodes of nerve palsy; axonal degeneration might be rarely associated. The myelin sausages are the markers of a selective vulnerability of the nerve fibers either to mechanical injury or to some other unknown event.