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The term Morvan's disease, first coined in 1890, is still in use, although the generic term neuromyotonia--which is not exempt from criticism--has largely superseded it. Symptoms and signs are variable, ranging from benign painful fasciculations, pseudomyotonic cases, rigid forms, cases in which central nervous system features are also present (with, in addition to nerve hyperexcitability, agitation, confusion, delirium, insomnia, hyperhidrosis and tachycardia). A distal peripheral motor nerve is the origin of nerve hyperexcitability. There is growing evidence that autoimmunity is involved in the pathogenesis of many cases. Antibodies to voltage-gated potassium channels are detected in the serum of many patients with peripheral nerve hyperexcitability. Other cases are probably genetic. Inherited disorders are related to episodic dominant ataxia type 1, with the same mutation of a gene coding for potassium channel subunit Kv 1-1. Many inappropriate or non specific names are used to refer to peripheral nerve hyperexcitability. Isaacs syndrome, voltage-gated potassium channelopathy, or Morvan's syndrome are suggested.

Seventy nine patients were admitted for syringomyelia. Fifty-nine had a malformative syringomyelia, 15 a post-traumatic syrinx and 5 a syringomyelia related to a meningitis. For all the patients, the diagnosis of syringomyelia was performed by MRI with measures of syrinx extension and transverse diameter. Posterior tibial somato sensory evoked potentials (PT SEP), median (M SEP), trigeminal (V3 SEP), brain stem auditory evoked potentials (BEAP), cortical and cervical motor evoked potentials (MEP) were correlated with clinical and radiological findings. SEP abnormalities were not correlated with the duration of symptoms. PT SEP proved to be more sensitive than M SEP, MEP abnormalities were very frequent (72% of the cases), even without clinical motor deficit. Trigeminal SEP were more sensitive than BAEP which were not related to the presence of associated cranio vertebral abnormalities. No significant relationship between clinical and radiological results was observed. There was a positive relationship between electrophysiological and radiological results. Nevertheless, a good correlation was observed between lateral clinical, MRI and electrophysiological results. Abnormal trigeminal SEP were detected in 46.6% of the patients with high cervical syringomyelia. In all cases, trigeminal SEP and MEP should be done in association with M and PT SEP as both of them detect subclinical evidence of spinal cord dysfunction in syringomyelia.

Twenty-seven patients (15 males, 12 females, age range: 16-66 years) were admitted for malformative syringomyelia diagnosed on MRI with measures of syrinx extending and transverse diameter. Posterior tibial somatosensory evoked potentials (PT SEP), median (M SEP), trigeminal (V3 SEP), brain stem auditory evoked potentials (BEAP), cortical and cervical motor evoked potentials (MEP) were correlated with clinical and radiological findings. SEP abnormalities were not correlated with the duration of symptoms. PT SEP proved to be more sensitive than M SEP. MEP abnormalities were very frequent (87% of the cases), even without clinical motor deficits. Trigeminal SEP were more sensitive than BEAP which were not related to the presence of associated cranio-vertebral abnormalities. We found no significative relationship between clinical and radiological results. Moreover, there was a positive relationship between electrophysiological and radiological results: abnormal trigeminal SEP were detected in 85% of the patients with high cervical syringomyelia. In all cases, trigeminal SEP and MEP should be done in association with M and PT SEP as both of them detect subclinical evidence of spinal cord dysfunction in syringomyelia.

Certain diffuse forms of myelitis may be due to raised intra-spinal venous pressure resulting in veritable "varicose veins of the spinal cord". The origin of this increased pressure is often multifactorial, but may be due to venous reflux of blood from the left kidney into the intraspinal plexuses via the reno-spinal trunk. Ligation of this trunk results in a considerable and often complete improvement in the neurological syndrome. This operation was performed for the first time by our team in 1973 and since then has been successfully performed on 30 occasions for 21 cases of myelopathy and 9 cases of syringomyelia.

Three cases of neuropathic leprosy (one Moroccan, two non-colonial immigrants) enable attention to be drawn to two aspects of theproblem of Hansen's neuritis: 1) such cases should no longer be considered exceptional, infection occuring in countries where leprosy is endemic but the disease developing years later in any country; 2) among the various neurological aspects of neuritis due to Hansen's bacillus, great stress is laid on sensory disorders of the syringomyelic type, with thermalgesic dissociation; although these symptoms have been considered typical (our three cases are an illustration of this), they seem to occur fairly rarely and are the cause of difficulties in diagnosis as it is the last thing one would think of. Treatment of these neural forms is not encouraging, in spite of a therapeutic arsenal which in theory is considered effective.