The Correlation Between Tremor Characteristics and the Predicted Volume of Effective Lesions in Stereotaxic Nucleus Ventralis Intermedius Thalamotomy

Abstract

In 51 cases (6 cases with bilateral operations) with various kinds of tremor, stereotaxic ventralis intermedius (Vim) thalamotomies were performed using Leksell's apparatus and the results of operation evaluated. Several characteristics of the tremor, including clinical features and EMG, were correlated with the assumed location and volume of the coagulative lesion. In 54 of the 57 operations, the thalamic Vim nucleus was identified physiologically and a therapeutic lesion placed at a site that included the Vim neurons. In all these cases, except one in which the lesion was estimated to be too small, tremor was immediately abolished by a relatively small lesion. The estimated volume of the lesion was about 40 to 200 mm3 and the effect persisted over a long follow-up period (maximum ten years). The size of the lesion that was necessary apparently depended on several features of the tremor. A larger lesion was required in cases of movement type tremor, tremor with a low rate (less than 4 Hz), tremor of high amplitude (more than 600 microV), and tremor involving proximal muscles or with a wide distribution. Tremor following a cerebrovascular lesion and post-traumatic tremor were characterized by coarse oscillation (high amplitude and low frequency) involving proximal muscles. A relatively larger coagulative lesion was therefore necessary to relieve this type of tremor. In contrast, parkinsonian and essential tremor were usually of low amplitude and distal in distribution. For the relief of such tremor, the lesion could be very small: if aided by electrophysiological methods to identify Vim neurons, the minimal effective volume of the lesion was estimated as about 40 mm3 and restricted to the Vim nucleus. Based on these results, the importance of the Vim nucleus in tremor mechanisms is discussed.

Deep brain stimulation in the subthalamic area is more effective than nucleus ventralis intermedius stimulation for bilateral intention tremor

“…In fact, several facts indicate that a proper target for (distal) resting and postural (Parkinsonian) tremor may not suffice for severe (proximal) intention tremor [3,8,28]. Correct targeting of the ventro-lateral thalamus has been reported to result in insufficient intraoperative tremor control [6,29,36,37,64], and superior effects on severe intention tremor in ET and MS have been ascribed to DBS in the posterior subthalamic white matter [3,36,45,48,53].…”

“…These favourable effects have been ascribed to the zona incerta, prelemniscal radiation (RAPRL), fields of Forel, but also the subthalamic nucleus [3,5,10,28,30,33,38,40,46,47,57,58,61,62]. Thus, clearly distinct stereotactic targets located several millimeters apart have been suggested to result in best tremor suppression.…”

Initial clinical manifestations of Parkinson's disease: features and pathophysiological mechanisms

“…However, rhythmic fi ring is better recorded and tremor stopped in the ventralis intermedius nucleus (Vim) of the thalamus. 66 The Vim is outside the basal ganglia projection territory; it receives propioceptive (type Ia) aff erents from muscle spindles and projects to the primary somatosensory cortex and motor cortex (area 3a). In monkeys treated with MPTP, 5 Hz stimulation of the GPi is not capable of recruiting and driving motor cortex activity, revealing a fi ltering characteristic of low frequency activity in the motor circuit.…”

Nonlinear interactions in the thalamocortical loop in essential tremor: A model-based frequency domain analysis

“…The central oscillating constituents of the network comprise parts of the physiological central motor system . There is both neurophysiological and clinical evidence of thalamic involvement in the central oscillatory network generating essential tremor (Hirai et al, 1983, Hubble et al, 1996, Marsden et al, 2000, Vaillancourt et al, 2003, Lyons and Pahwa, 2004, Hua and Lenz, 2005, Deuschl et al, 2011. Local field potential (LFP) recordings of thalamic ventralis intermedius (Vim) nucleus show strong linear correlation with the contralateral EMG during tremor (Marsden et al, 2000).…”