The aspects of trigemina! sensory structure and function which are uniquely different from spinal systems are reviewed in this paper.

In the periphery, several unique arrangements of sensory receptors are seen, and appear to have unique sensory functions. The receptors in the cornea, the nasal mucosa, and the tooth pulp are morphologically unspecialized and are associated with “protopathic” sensory experiences. The important sensory functions of the mammalian vibrissae are also discussed, as well as their relationship to the anatomically distinctive cortical “barrels”.

Aspects of trigeminal proprioception are also of interest. The absence of spindles in some muscles and the unique central organization of trigeminal proprioceptive afférents in the jaw and extraocular muscles are of functional significance in the motor function of the jaw and the eye.

Trigeminal afférents are also involved in several complex autonomie reflexes. Characteristic changes in cardiovascular and respiratory function are elicited by various patterns of trigeminal sensory stimulation. These reflexes include the diving reflex, the oculo-cardiac reflex, naso-cardiorespira-tory reflexes, and the trigeminal depressor response. The clinical significance of these reflexes is discussed.

Several coordinated behavioral responses including suckling are also elicited from trigeminal afférents. The evidence implicating trigeminal afférents in eating and drinking behavior is presented.

Effects of chronic denervation upon in vivo forearm metabolism were studied in six patients and six controls. The diagnosis was amyotrophic lateral sclerosis in four patients, the neuronal form of Charcot-Marie Tooth disease in one patient, and an unclassified chronic disease of the lower motor neurons in one patient. In all cases the forearm muscles showed clinical weakness and electrical evidence of denervation, while muscle biopsy from a proximal muscle of the upper limb showed typical denervation atrophy. At rest there was increased oxygen utilization and lactate output as well as a tendency for increased uptake of glucose and long chain fatty acids from arterial blood per 100 ml of f orear m tissue. During exercise the abnormally high lactate output increased further. An increased arterial lactate concentration was present during rest and exercise. Oxidation of fatty acids was not impaired. It is suggested that these abnormalities are consistent with an augmented utilization of blood borne fuels at rest by denervated muscles. A concurrent regional ischemia of muscles during rest and exercise, possibly due to defective autoregulation of skeletal muscle blood flow, may exlain the abnormally high lactate generation.

Unilateral lesions involving the area immediately caudal to the locus coeruleus in the cat are associated with slight decreases of noradrenaline (NA) in both sides of the spinal cord without any important change of serotonin (5-HT) concentration in the spinal cord and of N A and 5-HT concentrations in the cerebral cortex of both sides. In other cats with similar lesions involving the same area bilaterally (postlocus lesions) NA is markedly decreased and 5-H T slightly decreased in the hypothalamus and spinal cord but the concentrations of NA and 5-HT of the cerebral cortex, striât urn and thalamus are not conspicuously modified by such postlocus lesions.

Unilateral lesions in the area of the loci coeruleus and subcoeruleus in the rat are associated with a marked decrease of noradrenaline (NA) in the ipsilateral cerebral cortex without any important change of NA in the contralateral cortex and in the spinal cord of both sides. Under such conditions the concentrations of serotonin (5-HT) are not significantly modified in the cerebral cortex and spinal cord of both sides. NA and 5-HT concentrations of the cerebral cortex of both sides are unmodified by unilateral lesions of the cerebellar nuclei in the rat. In the latter group of animals slight increases of NA and 5-HT in the spinal cord are significant in comparison to the values obtained in the control animals but not from one side of the spinal cord to the other.

These results further support the suggestion that the noradrenergic coeruleo-cortical pathway originating in the loci coeruleus and subcoeruleus ascends on the same side and ends in the ipsilateral cerebral cortex. In the light of the results of this investigation and of those reported in a companion paper (Marchand et ai, 1979) NA fibers reaching the hypothalamus and spinal cord most likely arise from neurons located caudally in respect to the locus coeruleus. Moreover NA fibers ending in the hypothalamus do not ascend in the dorsolateral part of the isthmic area and, therefore, have a different course than the N A fibers reaching the cerebral cortex and thalamus.

A case of progressive multi-focal leukoencephalopathy (PML) with selective involvement of cerebellum and brain stem is compared with nine other published cases. Recognition of PML presenting with ataxia before cerebral manifestations is stressed especially, since promising results with some antiviral drugs have been claimed.

Significant susceptibility to photically induced seizures has in the past been observed only in Senegalese baboons (Papio papio) and epileptic humans. However, we have unexpectedly observed a phot omy oclonic response to intermittent photic stimulation in 5 of a sample of 6 yellow baboons (Papio cynocephalus).

This retrospective study concerning 102 patients was undertaken to study the therapeutic decisions in these patients when they presented with symptoms of cerebral vascular insufficiency, mostly from the territory of the carotid artery, either transient or accompanied by a deficit. The current literature on the subject is also mentioned. The clinical outcome with regard to the quality of life, seems to have been better in patients who were subjected to carotid endar terectomies than in those who received medical treatment.

This case report describes a melanin-containing neurofibroma involving a spinal nerve root. Electron microscopy of the tumor shows that neoplastic Schwann cells are capable of melanogene-sis. Although this capability is suggested in the literature, few reports provide ultra-structural confirmation.

The likely identity between reported “cellular blue nevi of spinal nerve roots” and nerve sheath tumors is discussed. It is possible that pigmented nerve sheath tumors behave more aggressively than nonpigmented ones, although it is debatable.

A study of 17 parents (obligate hétérozygotes) of children with Friedreich's ataxia was carried out. In addition to medical histories and physical examinations, a standard 12 lead ECG tracing was obtained. In the age group below 50, there was no significant evidence of ischaemic or primary cardiomyopathy. Older subjects had more frequent risk factors for arteriosclerotic heart disease.

The evolution of 15patients initially evaluated during Phase One of the Quebec Cooperative Study of Friedreich's ataxia has been studied approximately three years later. It is concluded that the deterioration of cardio-pulmonary function in Friedreich's ataxia is multi-factorial. The neuromyopathy (or the underlying metabolic or cellular defect) appears to be the main contributing factor to the deterioration of cardio-pulmonary function, which is exacerbated by the scoliosis and varying severity of the cardiomyopathy.

Friedreich's Ataxia (F.A.) is a degenerative disease which commonly leads to premature death of cardio-respiratory origin. To explain the early death of these patients, previous investigations have established the existence of I) a cardiomyopathy in nearly 100% of cases, 2) a restrictive pulmonary syndrome of scoliotic origin and 3) a mild hypoxemia associated with slight respiratory alkalosis and a normal oxyhemoglobin dissociation curve. To further assess the cause of early death in patients with such neuromyo-pathy, we evaluated, in eleven FA. patients, the sensitivity of the respiratory centers to hypercapnia, hypoxia, and hyperoxia.

Ventilatory (VE, VT, F, VT/Ti) and occlusion pressure (P0.1) responses were taken as indices of the respiratory centers output during progressive hypercapnia (Read's method) and isocarhic hypoxia (Weil's method). We studied lì Friedreich's Ataxia patients and II age, sex, and arm-span matched controls. The responses of patients to hypercapnia were significantly greater than controls hut their responses to hypoxia were similar to controls.

Our study establishes that the respiratory centers are functioning adequately in early Friedreich's Ataxia and do not contribute to cardio-respiratory insufficiency in such neuromyopathy.

A clinical neuro-opthalmo-logical and electro-oculographic study was made on fourteen patients with Friedreich's ataxia. None had evidence of optic nerve dysfunction. No patient complained of oscillopsia although all had ocular motor deficits of varying degrees, which appeared to be related to the severity of the general manifestations of the disease. The defects comprised square wave jerks, jerky pursuit with inability to maintain eccentric gaze resulting in gaze paretic nystagmus and rebound nystagmus. There was failure to suppress by fixation the vestíbulo-ocular reflex. The slow phase velocity of caloric nystagmus was always of reduced velocity. There was inability to augment the slow phase velocity of optokinetic nystagmus with increasing stimulus velocity. Abnormalities of the saccadic system were manifest particularly as hypermetria. These signs in combination are suggestive of disease involving the cere be I lar flocculus and vermis or their brain stem connections. No abnormalities were found in 17 parents or siblings.

An estimate is given of the frequency of pathological changes (assessed by cell populations and from myelin staining) in the brains of 15 cases of Friedreich's ataxia. Mention is made of the special problem of distinguishing primary degenerative lesions from those due to circulatory disturbances arising from the patients cardiac disease.

Electronystagmographic recordings were made of oculomotor and vestibular function in II patients with autósomat recessive spastic ataxia of Charlevoix-Saguenay. All had horizontal gaze nystagmus, marked impairment of smooth ocular pursuit and optokinetic nystagmus, and defective fixation suppression of caloric nystagmus. Many had saccadic dysmetria. but saccade velocity was probably unaffected. Abnormallies pointing to brainstem disturbance were sparse. The findings are thought to indicate mainly diffuse cerebellar disease, with particular involvement of vermis and vestibulo-cerebellum.

Twenty four ataxie patients were investigated with electromyography and nerve conduction studies. They were divided in two groups according to the area they came from, the evolution of the disease, and the clinical signs. Group I patients from the Rimouski area displayed all the clinical and electrophysiological signs of Friedreich's ataxia. Group II comprised patients who presented with a new syndrome known as the autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Although the clinical evolution was better in the latter, there were more electromyographic signs of denervation and the motor conduction velocities were slower. Both groups showed identical and important abnormalities in sensory nerve conduction.

The results of electrophysiological studies in spastic ataxia have not been reported to our knowledge. They underline the place of spastic ataxia as distinct f rom Friedreich's ataxia, spastic paraplegia, and the known familial neuropathies.

Electroencephalographie studies have heen done in two groups of hereditary ataxia: a group hearing the classical features of Friedreich's ataxia and a group clinically different described as autosomal recessive spastic ataxia of Charlevoix-Saguenay (A RSA CS). The qualitative anomalies observed in the two Ķroups were similar and were comparable with the data reported in the literature. However, the main difference between the two groups is the greater incidence of EEG abnormalities in the A RSA CS group, which suggests more involvement of the cortical and subcortical structures. This is reinforced by the lower I.Q. performance in the latter patients. Some comments are made about focal EEG findings, behavior and I.Q. In general, EEG was not considered a valuable instrument for diagnosis since no qualitative electric pattern could be identified. With regard to prognosis, EEG cannot be used as a criterion, since there is no relation between the degree of anomalies and the severity of the disease and since EEG does not worsen with the progression of the disease.

Nine cases of Friedreich's ataxia and seven cases of autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) were submitted to neuroradiological procedures to determine the extent of atrophie processes in the central nervous system. All cases had a computerized cerebral tomography and five were studied with pneumencephalo-graphy. The results show a correlation between the two tests and the comparison between Friedreich's ataxia and ARS ACS.

In Friedreich's ataxia, the radiological signs are variable and discrete in most of the cases. In A RSA CS there are constant signs of cerebellar atrophy almost limited to the superior parts of the vermis and anterior lobes.

Two female patients aged 30 and 40 years with the Charlevoix-Saguenay ataxia were studied. Both had absent sensory action potentials in upper and lower extremities but, unlike typical cases of Friedreich's ataxia, they displayed a marked slowing of motor conduction velocities. Sural nerve biopsies taken from calf and ankle revealed a severe loss of large my elina ted axons contrasting with a normal myelinated fiber density. Evidence for active axonal degeneration was scarce, with no indication of axonal regeneration.

Teased myelinated fibers revealed an increased variability of internodal length but no evidence for myelin breakdown. These findings support, as a primary defect, a developmental abnormality of peripheral nerve, namely a lack of maturation of large myelinated axons and possibly a faulty myelination of nerve fibers. We think it is unlikely to represent a progressive axonal atrophie or dystrophic process, as suggested in Friedreich's ataxia.

We described a cluster of 8 independent sibships of Friedreich's ataxia in the ShFabien parish of Rimouski and have shown that they are all related within 6 generations. The study of this geographic and genetic isolate permitted the investigation of certain unusual features of the disease such as constant myopia, delayed reaction times to pain, flexor spasms, anda rapid evolution.

The purpose of the present study was to design a standard battery of tests capable of quantitatively characterizing ataxia and concomitant neurological signs in the rat. In addition to a systematic analysis of the walking gait of animals, tests for activity, catalepsy, rigidity, and various reflexive responses were included in the battery. The standardization and validation of the test system was performed by determining and comparing profiles of neurobehavioral effects produced by 3-acetyl pyridine, acrylamide, pyrithiamine, and thiamine deficiency, four experimental treatments reported to induce ataxia in animals. Results indicate that profiles of neurobehavioral disturbances accompanying ataxia in animals varied distinctively with each experimental treatment.