The Croonian Lectures ON THE CLINICAL SYMPTOMS OF CEREBELLAR DISEASE AND THEIR INTERPRETATION.

Transcranial magnetic stimulation (TMS) over the leg motor area elicits a soleus primary response (SPR) and a soleus late response (SLR). We evaluated the influence of the cerebellofugal pathway on the SPR and SLR in patients with ‘pure’ cerebellar ataxia.

SPRs and SLRs were recorded from 11 healthy subjects and 9 patients with ‘pure’ cerebellar cortical degeneration; 5 with spinocerebellar ataxia type 6 (SCA6), and 4 with late cortical cerebellar ataxia (LCCA). In addition, three patients with localized cerebellar lesions were tested.

The SPR latency was significantly longer in patients than in controls, but primary responses in the tibialis anterior muscle were normal. The frequency of abnormal SLR was 38.9% in the supine position and 83.3% in the standing position. Two out of three patients with localized cerebellar lesions also showed abnormal SLR.

Altered SPRs in patients may result from a dysfunction of the primary motor cortex caused by crossed cerebello-cerebral diaschisis. In addition, our results suggest that ‘pure’ cerebellar degeneration involves the mechanism responsible for evoking SLR which is related to the control of posture.

SLR can be a useful neurophysiological parameter for evaluating cerebellofugal function.

Cerebellar mutism (CM) is a postoperative complication of mainly pediatric posterior fossa surgery. Multiple theories exist for explaining this phenomenon. We have made an attempt to further understand this entity given a particularly interesting case as it relates to multiple pathophysiologic pathways.

We have reviewed the details surrounding a particularly interesting case of CM. A retrospective analysis of this patient's clinical history and recovery is described. An extensive literature review has been performed in conjunction with an attempt to help elucidate details and a better understanding of CM.

A thorough analysis of existing theories as to the pathophysiologic mechanism of CM has been performed as it relates to the details of this particular case. A case is described in which a child exhibiting CM abruptly improved and made a relatively quick recovery after the triggering of the melodic speech pathway by way of watching and beginning to sing along with a video. It appears that this incident involving a familiar song catalyzed various speech pathways, which apparently were in some state of shock. This phenomenon seems to be a temporary entity involving not only the mechanical coordination of speech production, but also the initiation of speech itself.

Evidence exists for a pathophysiologic pathway for speech by way of coordinating phonation and articulation. In addition, there seems to exist a pathway by which the initiation of speech may be altered or halted by posterior fossa pathology, namely, vermian or dentate nuclear injury. In particular to this case, we found that the incidental appreciation of other forms of speech, melodic in this instance, may be the key to help stimulate and accelerate the recovery from CM.

We have studied multi-joint arm movements in a patient with right cerebellar damage. Our patient's kinetic tremor was reduced in the absence of visual feedback, but increased when performing a concurrent cognitive task. We suggest that her kinetic tremor reflects use of a slow cortical feedback circuit for error-corrections during movement. Analysing the spatial relation between hand aperture and hand transport in prehensile movements, we found preserved strategic, trial-to-trial coordination, but impaired reactive, within-trial coordination. We conclude that the proprioceptive representations provided by the normal cerebellum play an important role in coordinating multi-joint movement.

Transient mutism, without disorders of consciousness or cranial nerve deficits, arising after surgical operations on the posterior cranial fossa is a recently described entity.

To date 22 cases have been reported, to which we add the present case (the first report of the syndrome in an adult).

We review the salient features of the syndrome in the light of the published cases and speculate on the underlying physiopathology.

Profound truncal ataxia, dysmetria, postural tremor of the head, trunk and limbs and hypotonia and intention (acting) tremor of the limbs were displayed by 3 monkeys with total cerebellectomy and 2 monkeys with extensive damage to several structures of the cerebellum. Truncal ataxia, dysmetria, hypotonia and intention tremor gradually diminished during the immediate postoperative period whereas postural tremor became less conspicuous. The administration of harmaline, however, exaggerated or evoked postural tremor of the limbs and trunk for a period of 3–4 hr in these monkeys.

On the one hand lesions of the vermis of the posterior lobe and of part of the nodulus in one animal or of the interpositus and fastigial nuclei of both sides and the nodulus in another animal or destruction of the uvula and the interpositus nuclei associated with partial involvement of dentate and fastigial nuclei of both sides in a third animal resulted in truncal ataxia and transient dysmetria. The latter animal repeatedly displayed postural tremor of the two upper limbs in response to harmaline. Harmaline, however, did not produce any peculiar effect in the 2 former animals. On the other hand unilateral or bilateral lesions of the dentate and interpositus nuclei or destruction of the left half of the posterior lobe (with or without involvement of the corresponding dentate nucleus) or interruption of the superior cerebellar peduncle did not result in any marked and/or sustained motor impairment. Nine out of 10 monkeys with such lesions, however, displayed postural tremor of the ipsilateral limbs after the administration of harmaline.

Truncal ataxia predominantly involves a disturbance of the uvula and nodulus and/or the fastigial nuclei and their interconnections with the vestibular nuclei and, most likely, with the dorsal and medial accessory olives. Dysmetria (or incoordination of the limbs) is apparently related to a combined impairment of structures of the anterior and posterior lobes of the cerebellum and their corresponding interconnections with the cerebellar nuclei. Postural tremor is partly related to a disturbance at the level of a series of phylogenetically more recent structures including parts of the principal olive, neocerebellar cortex and dentate nucleus and the parvocellular division of the red nucleus as well as their nervous interconnections.

La cérébellectomie totale ou sub-totale s'accompagne d'ataxie tronculaire grave, de dysmétrie des membres, de tremblement postural de la tête, du tronc et des membres ainsi que d'hypotonie et de tremblement d'action intéressant surtout les membres supérieurs. L'ataxie tronculaire, la dysmétrie et l'hypotonie régressent durant la période postopératoire tandis que le tremblement postural et le tremblement d'action deviennent presque imperceptibles. Par contre l'administration d'harmaline à ces animaux exagère le tremblement postural déjà existant ou le provoque. D'une part la destruction du vermis du lobe postérieur et du nodule ou des deux noyaux interposés et fastigiaux ou l'atteinte bilatérale et partielle des trois noyaux du cervelet s'accompagne d'ataxie tronculaire et de dysmétrie se manifestant transitoirement. Par contre l'harmaline administrée `a 3 singes porteurs de lésions des noyaux du cervelet n'induit du tremblement postural que chez l'un d'entre eux où la lésion touche les noyaux dentelés. D'autre part l'atteinte uni- ou bilatérale des noyaux dentelé et interposé ou la destruction de la moitié gauche du lobe postérieur (avec ou sans atteinte du noyaux dentéle correspondant) ou, encore, l'interruption du pédoncule cérébelleux supérieur n'entraîne aucun déficit moteur grave et/ou permanent. Cependant 9 des 10 singes porteurs de telles lésions ont accusé du tremblement postural des membres ipsilatéral en réponse à l'harmaline.

L'ataxie tronculaire implique primordialement l'atteinte de l'uvule et du nodule et/ou des noyaux fastigiaux et de leurs interconnexions avec les noyaux vestibulaires et, selon toute évidence, avec les olives accessoires médianes et dorsales. La dysmétrie ou incoordination des membres semble reliée à l'atteinte de structures des lobes antérieur et postérieur du cervelet et de leurs interconnexions avec les noyaux du cervelet. Le tremblement postural (ou de repos) met en cause un ensemble de structures phylogénétiquement plus récentes localisées au niveau de l'olive principale, du néocortex du cervelet et du noyau dentelé en plus du noyau rouge (division parvicellulaire) et leurs interconnexions nerveuses.

Monkeys were trained to perform simple motor habits including phasic movement and maintained limb positions before receiving bilateral lesions of the cerebellar dentate and interpositus nuclei. The frequency, relative amplitude, and duration of oscillations, measured by an accelerometer worn on the limb, varied with the limb's position, being slower and wider (ataxia) with more extended-abducted positions, faster and smaller (tremor) with more flexed-adducted postures. Changes with time showed a progressive conversion of ataxic oscillations to tremor as reflex and locomotor performance improved. At any time, limb fixation combined with phasic movement initiated the oscillations, whereas a fixed position by itself could be maintained, or a phasic movement without a fixed end point performed without tremor or ataxia. Analysis of these data suggests that the cerebellum provides a timing device for movement which matches limb fixation with phasic (usually distal) movement so that the limb fixation stops at the right moment for the phasic component to begin. The timing of these two components may have separate mediation by the interpositus (fixation) and dentate (phasic-distal) nuclei. During recovery, loss of internal feed-forward cerebellar circuits is compensated for by external feedback loops involving the dorsal root afferents and cerebral cortex.