Peripheral and central conduction times in hereditary pressure-sensitive neuropathy

Hereditary neuropathy with liability to pressure palsies: a clinical, electroneurophysiological and morphological study

Clinical, electroneurographic and myographic studies were performed on 99 patients of 13 families having hereditary neuropathy with liability to pressure palsies (HNPP) and on 116 relatives. Diagnosis was confirmed in all families by a nerve biopsy of the index case. Large focal myelin thickenings (tomacula) were found in nerve biopsies of affected persons, whether or not pressure palsies had occurred. By using three electroneurographical parameters it was possible to discriminate between asymptomatic patients and unaffected relatives. Complaints sometimes mentioned in literature as being associated with HNPP such as low back pain, brachialgia and short lasting paraesthesia are not related to HNPP. The hereditary transmission is autosomal dominant with total penetration but variable expression.

Clinical and electrodiagnostic findings, nerve biopsy and blood group markers in a family with hereditary neuropathy with liability to pressure palsies

Clinical, electrophysiologic and biopsy findings as well as studies of blood group markers in a family with hereditary neuropathy with liability to pressure palsies (HNPP) are reported. There was an autosomal dominant trait without genetic linkage between the HNPP gene and blood group markers controlled by chromosome 1. Reduced motor and sensory nerve conduction velocity was found in clinically affected and unaffected nerves. Characteristic morphological changes in sural nerve biopsy including tomaculous swelling were present.

Recurrent familial neuropathy due to liability to pressure palsies

Two families with hereditary neuropathy with liability to pressure palsies (HNPP) were evaluated clinically, electrophysiologically and pathologically (2 index cases). Familial patterns suggest autosomal dominant inheritance. The clinical presentation is characteristic, with recurrent painless transitory mononeuropathy, without evident triggering factors, or caused by trivial trauma or pressure. In affected members neurophysiological studies showed diffuse slowing in nerve conduction, more evident at common sites of entrapment. Somatosensory evoked potentials (SEPs) showed bilateral peripheral abnormalities with proximal nerve involvement more pronounced in older patients. 40 to 75% of teased fibers displayed sausage-shaped swellings. Ultrastructurally some sausages showed redundant myelin loops and excessive number of myelin lamellae that seem to cause axonal constriction.

The neuropathy resulting from muscle-nerve translocation

The biceps femoris muscle was cut close to its distal tendon in seventeen rats, inserted under the partially freed sciatic nerve and the muscle then resutured leaving the nerve in a translocated position. The rats were killed at intervals from 4 to 22 weeks later and the sciatic nerve above, around, and below the muscle reflection site examined by light and electron microscopy and teased fibre preparations. In all cases, the sciatic nerve was affected to varying degrees at its reflected site ranging from focal sub-perineurial demyelination and remyelination to widespread myelin sheath abnormalities. Teased fibre studies confirmed that the myelin sheath was predominantly affected with little evidence of active axonal degeneration. There was no proximal and minimal distal sciatic nerve damage. The most likely cause of these changes was thought to be focal compression but the possible role of other factors is also discussed.

Hereditary neuropathy with liability to pressure palsies. Report of two families and review of the literature

Clinical, neurophysiological and pathological investigations were carried out in 11 affected members of 2 families with hereditary neuropathy with liability to pressure palsies (HNPP). The observations were related to findings in 261 cases of 47 families published in the literature. It was concluded that HNPP is a nosological entity characterized by the following diagnostic criteria: (1) an autosomal dominant inheritance; (2) the clinical presentation of a recurrent mononeuropathy simplex or multiplex, frequently related to an inadequate trauma to peripheral nerves; (3) a significant slowing of motor and sensory conduction velocity in clinically affected, but also in clinically unaffected nerves; (4) characteristic morphological findings in sural nerve biopsy featuring "tomaculous" swellings of myelin sheaths, transnodal myelination and segmental demyelination. The pathogenesis of HNPP is not clear. Hypothetical explanations of the pathogenesis of HNPP are discussed.

Somatosensory tibial nerve evoked potentials with parasagittal tumours: a contribution to the problem of generators

Somatosensory evoked potentials following stimulation of the median nerve at the wrist and the tibial nerve at the ankle were recorded in 5 patients with parasagittal tumours, 4 in the fronto-parietal and 1 in the frontal region. Three had intracerebral tumours and 2 parasagittal meningiomas. The extent of each lesion was determined by CT scan, showing a unilateral process involving predominantly the paracentral lobule and adjacent parts of the post- and precentral gyri ("Mantelkante') in 4 patients and a more frontal location of one meningioma affecting mainly the superior frontal gyrus. SEPs recorded from the patients with fronto-parietal tumours showed a uniform pattern with a complete absence of the wave N70 of the tibial SEP elicited by stimulating the nerve contralateral to the lesion. All other waves, including the P40-N50 complex on both sides and the median SEP, were in the normal range. In contrast, the frontal meningioma led to an only slightly altered from of the waves immediately following the initial P40-N50 complex. It is concluded that the tumour abolished the generators of the wave N70 which are apparently located in the cortical somatosensory leg area. Therefore unilateral loss of the wave N70 is indicative of parasagittal lesions. The results may give good evidence that the P40-N50 complex is generated in the thalamus or thalamo-cortical connections.