SUMMARY Three cases of unilateral dystonia of vascular origin are presented and compared with those in the literature. Damage in the region of the lenticulostriate arteries accounted for ischaemic lesions of the putamino-capsulo-caudate region, the external pallidum probably also being involved. This syndrome appears if the ischaemic accident took place during childhood. The functions of each of these structures and the possible role of the anterior limb of the internal capsule are discussed.Dystonia represents a particular group of diseases involving the motor system. Denny-Brown' defined it as "a fixed or relatively fixed attitude in association with other extrapyramidal disorders of movement". Dystonia musculorum deformans is its major form, but the absence of specific pathology in this condition makes any physiopathological interpretation particularly difficult.2 However, besides this idiopathic, occasionally hereditary3 form of the disease, dystonic syndromes can occur in metabolic,4 anoxic,5 tumoural6 and infectious disorders.7 Dystonia of vascular origin is particularly interesting, because the responsible lesions may be more limited than those of metabolic or anoxic origin, thus permitting speculation on the pathological-anatomic basis of this unique motor disease. Vascular dystonia usually is unilateral, and frequently, but not necessarily, follows a hemiplegia.' 8-15 We report three cases in which the CT scan enabled us to diagnose the obliteration of a lenticulo-striate artery, causing lesions in the putamen, to the head of the caudate nucleus and to the anterior limb of the internal capsule. Case ReportsCase I A 3-year-old child without any medical, surgical or family history, had a mild head injury without loss of consciousness in 1967; 15 minutes later, the parents Address for reprint requests: Prof P Rondot,

The pathogenesis of posttraumatic subdural hygroma still remains largely unknown. One of the suggested pathological mechanisms is the traumatic development of an arachnoid tear and the subsequent efflux of CSF into the subdural space. We performed a multifactorial analysis of the hygroma fluid obtained at operation in comparison to the simultaneously taken plasma and lumbar CSF. The results of the protein analysis support the CSF origin of the subdural hygroma fluid.

The clinical course of 11 patients with a subdural hygroma, who underwent neurosurgery, was studied. In the first week after the operation no improvement of the mental status could be detected. We considered therefore that operation hardly contributed to improvement. Thus the need to operate is limited to special cases such as acute or space-occupying subdural hygroma.

Electrically evoked short latency vestibular potentials were recorded in 9 patients during vestibular neurectomy. Patients were operated on because of intractable Meniere's disease. The VIIIth cranial nerve was exposed through a limited retrosigmoidal approach; the vestibular nerve was contacted in the cerebello-pontine angle with a bipolar platinum-iridium electrode and stimulated with biphasic current pulses (100 microseconds/phase, 0.75-1 mA p-p, 20/s). The responses were recorded over 12.8 ms between a forehead and an ipsilateral ear lobe electrode. Each recording consisted of 2 x 1,000 averaged responses. A systematically reproducible vertex-negative potential occurring at a latency of approximately 2 ms and having an amplitude of approximately 0.5 microV was recorded in all patients. This vertex-negative potential disappeared after selective vestibular neurectomy proximal to the stimulation site. Simultaneous continuous acoustic masking did not affect the response and no facial nerve response was observed on the facial nerve monitoring. These features strongly suggest that the characteristic vertex-negative potential constitutes a specifically evoked response of the vestibular system. Electrophysiological monitoring of the sectioning of the vestibular nerve during operation is one possible clinical application of intraoperative recording of electrically evoked vestibular potentials.

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