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The literature on thalamic surgery is difficult to read because different nomenclatures are in use. Neurosurgeons mostly use the stereotactic atlas of Schaltenbrand with Hassler's nomenclature of the thalamus. Neuroanatomists use different nomenclatures for the primate thalamus. The cytoarchitectonic definition of nuclei is difficult in the motor thalamus, and it would be best to define the nuclei based on their subcortical afferents. However, tracing studies are not available in humans. Thus, human thalamic nomenclature is based entirely on cytoarchitectonic subdivisions and transfer of knowledge by analogy from monkey to man. Problems arise when trying to transfer the detailed knowledge from monkey to the human brain. By doing so, different authors have come to different conclusions concerning the subcortical afferents of Hassler's motor nuclei, which inevitably leads to confusion when attempting neurophysiological interpretations of the surgical data. The present review draws attention to the discrepancies and open questions in the literature. There is a need to better define the limits of the sensory and cerebellar afferent receiving thalamic nuclei as well as those of the cerebellar and pallidal afferent receiving territories in humans. © 2002 Movement Disorder Society

Studying the clinical effects induced by electrical stimulation of the subthalamic nucleus (STN) area in a parkinsonian patient under local anesthesia is a mandatory step to determine the precise location of the final chronic electrode. Using multiple microelectrodes, preferably in a concentric parallel array allows a precise mapping of the STN region. The most reliable features to determine the suitable target are stimulation‐induced dyskinesias and rigidity decrease at a low intensity without adverse effects or only at far higher intensities. New skills are needed to assess all stimulation‐induced effects and interpret them in anatomo‐functional terms. © 2002 Movement Disorder Society

Deep brain stimulation for severe dystonia is still in the very first stage of development. Only single case reports or small case series have been reported to date. Best results have been obtained with pallidal stimulation in patients with primary generalised dystonia, especially in DYT1 mutation carriers. In secondary dystonia, conflicting results were reported. However, there is today enough promising evidence for a striking efficacy of pallidal stimulation in dystonia, supporting the need for further investigations in the field, with collaborative projects (regarding to the limited number of eligible patients); double‐blind studies, including a consensus about surgical method; and a precise anatomic analysis of the position of the electrode. A careful assessment of the efficacy by using improved clinical scale is also warranted. © 2002 Movement Disorder Society

Microelectrode recordings of single unit neuronal activity were used during stereotactic surgery to define the subthalamic nucleus for chronic deep brain stimulation in the treatment of Parkinson's disease. By using five parallel trajectories, often two to three microelectrodes allow us to recognize subthalamic nucleus (STN) neuronal activity. STN neurons were easily distinguished from cells of the overlying zona incerta and the underlying substantia nigra. During a typical exploratory track, we can observe a very low background noise in the zona incerta and almost complete absence of single cell recording. Penetration of the electrode tip into the STN is characterized by a sudden increase in background activity and single cell activity of spontaneously active neurons. The exit of electrode tip out of the STN corresponds to a decrease in background noise and a loss of single cell activity. Spontaneous neuronal activity increases again when the electrode tips enters the substantia nigra pars reticulata (SNr); however, the activity is less rich than in the STN, indicating a more cell‐sparse nucleus. STN neurons are characterized by a mean firing rate of 42.30 ± 22.00 spikes/sec (mean ± SD). The STN cells exhibited irregular or bursty discharge pattern. The pattern of single cell activity in the SNr is a more regular tonic activity that can easily be distinguished from the bursting pattern in the STN. The most useful criteria to select a trajectory are (1) the length of an individual trajectory displaying typical STN activity, (2) the bursting pattern of activity, and (3) motor responses typical of the sensorimotor part of the nucleus. In conclusion, microelectrode recording of the subthalamic area improves the accuracy of targeting the STN. © 2002 Movement Disorder Society

The postoperative neurologic management of patients with deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson’ s disease is a complex dynamic process that involves a progressive increase in stimulation intensity and a parallel decrease in antiparkinsonian medication while assessing the interactions of both treatments. Neurologists responsible for postoperative management of patients receiving STN DBS must have expert knowledge of the electroanatomy of the subthalamic area and be familiar with the medical treatment of motor and nonmotor symptoms, including the management of long‐term complications of levodopa treatment. Neurosurgeons who perform DBS need to understand the principles that guide the postoperative adaptation of treatment. This article defines guidelines for setting stimulation parameters, adapting drugs and managing adverse effects. © 2002 Movement Disorder Society

Deep brain stimulation (DBS) is a neurosurgical treatment of Parkinson's disease that is applied to three targets: the ventral intermediate nucleus of the thalamus (Vim), the globus pallidus internas (GPi) and the subthalamic nucleus (STN). Vim DBS mainly improves contralateral tremor and, therefore, is being supplanted by DBS of the two other targets, even in patients with tremor dominant disease. STN and GPi DBS improve off‐motor phases and dyskinesias. There is little comparative data between these procedures. The magnitude of the motor improvement seems more constant with STN than GPi DBS. STN DBS allows a decrease in antiparkinsonian drug doses and consumes moderate current. These advantages of STN over GPi DBS are offset by the need for more intensive postoperative management. The DBS procedure has the unique advantage of reversibility and adjustability over time. Patients with young‐onset Parkinson's disease suffering from levodopa‐induced motor complications but still responding well to levodopa and who exhibit no behavioral, mood, or cognitive impairment benefit the most from STN DBS. Adverse effects more specific of the DBS procedure are infection, cutaneous erosion, and lead breaking or disconnection. Intracranial electrode implantation can induce a hematoma or contusion. Most authors agree that the benefit to risk ratio of DBS is favorable. © 2002 Movement Disorder Society

We report three patients with bilateral GPi stimulation for stage 4 Parkinson's disease (PD) with severe levodopa‐induced dyskinesias (LID). In all three it was possible to completely inhibit LID using high‐stimulation parameters. Parallel to complete inhibition of LID, an inhibition of the anti‐akinetic effect of levodopa was observed, whereas, at the same time, rigidity was markedly improved. GPi stimulation is adaptable over time, and stimulation parameters have to be programmed according to off‐and on‐period motor symptoms. The main interest of stimulation is the possibility of finding a compromise between LID alleviation in on‐phase without loss of the beneficial motor effects and improvement in parkinsonism in off‐phase. In some patients, residual dyskinesias have to be accepted so as not to aggravate on‐period motor symptoms by a presumed overinhibition of basal ganglia outflow.

Retrocollis and opisthotonic posturing are typical clinical features of tardive dystonia and may be extremely disabling. We have treated five such patients with a custom‐made mechanical device that delivers constant contact to the occiput and shoulders. All patients experienced relief and their walking improved. This geste device, working like a geste antagonistique, may be useful for the management of some patients with severe axial dystonia with retrocollis and back arching.