[Neuronal activity of ventrolateral thalamus in patients with essential tremor].

OBJECTIVE

To investigate the neuronal activity in the ventrolateral thalamus in relation to essential tremor (ET).

METHODS

Microelectrode recording in the ventral oral posterior (Vop) and ventral intermediate nucleus (Vim) of thalamus was performed on 10 patients with ET and 10 patients with Parkinson's disease (PD) who underwent thalamotomy for tremor during operation. Electromyography (EMG) was carried out on the contralateral limbs simultaneously. Single unit analysis was performed to measure the interspike interval (ISI) and histogram was constructed to evaluate the pattern of neuronal activity. Student t-test was employed to compare the mean spontaneous firing rate (MSFR) and ISI of neuronal firing in Vop/Vim between the ET patients and PD patients. and correlation test.

RESULTS

Two hundred and sixty-six neurons were identified from 20 trajectories, 38.0% being neurons with tremor-related neuronal activity Tremor cells, 31.9% of neurons related to tonic firing, and 30.1% of neurons related to irregular discharge. 131 of these thalamic neurons, were obtained from 10 ET patients. 38 of these 131 neurons (29.0%) were related to tremor-related neuronal activity, 54 (41.2%) neurons were related to tonic firing with a mean spontaneous firing rate (MSFR) of (55+/-21) Hz, and 39 neurons (29.8%) were related to irregular discharge with a MSFR of (32+/-17) Hz. In the meantime, 135 neurons were obtained from 10 PD patients. Of these 135 neurons 63 (46.7%) were related to tremor, 31 neurons (23.0%) related to tonic firing with a MSFR of (39+/-15) Hz, and 41 (30.3%) were related to irregular discharge with a MSFR of (21+/-8) Hz. The MSFR levels of pooled neurons in Vop/Vim with tonic firing and irregular discharge of the ET patients were significantly higher than those of the PD patents (t=2.74 and 2.99, both P<0.05). And the MSFR levels in Vop and Vim of the ET patients were significantly higher than those of the PD patients (both P<0.05).

CONCLUSION

Vim receives the projection from cerebellum. The increase of neuronal firing frequency observed in Vim suggests that the pathophysiology of ET may be correlated with excessive activity of cerebellum.