Following earlier stereotactic experiences, we re-explored the possibilities of a therapeutic lesion of the pallidothalamic tract in the fields H1 and H2 of Forel in patients with parkinsonian signs. The physiopathological rationale of the pallidothalamic tractotomy (PTT) is based on the presence in the parkinsonian brain of a state of thalamic overinhibition due to an increased output of the internal pallidum. This causes the development of a thalamocortical dysrhythmia characterized by increased low frequencies in the relevant thalamic and frontal cortical areas. The fields of Forel are strategically placed to control this thalamic overinhibition, as they give passage to the majority of the pallidothalamic fibres. Magnetic resonance- and microelectrode-guided stereotactic PTT was proposed to 21 parkinsonian patients (mean age: 60 ± 10 years; mean Hoehn and Yahr in on-condition: 3.5 ± 1; mean disease duration: 11 ± 5 years). At a follow-up of 14 ± 6 months and in on-medication condition, a significant (P < 0.001) postoperative improvement of the motor part of the UPDRS (64.6%) and of the activities of daily living (ADL; 75.8%) was observed. Rest tremor, on-chorea and rigidity were reduced by 77.9, 92.2 and 82.3%, respectively. Distal and axial hypobradykinesias showed an improvement of 72.9 and 64%, respectively. Gait and postural stability also improved (57.5 and 66%, respectively) but at a lower level of significance (P < 0.005). Voice was not statistically influenced. L-dopa intake was decreased by 52.2% (P < 0.001) and 33% of the patients could be freed from treatment. In conclusion, PTT is an effective treatment for chronic therapy-resistant Parkinson's disease, improving symptoms in both on- and off-conditions.

Reactualization of the medial thalamotomy, performed since the fifties in cases of neurogenic pain, has been guided by the discovery of low threshold calcium spike bursts at frequencies in the delta-theta range in the posterior part of the central lateral (CL) nucleus. This thalamic rhythmicity is transmitted to the cortex through thalamocortical resonant properties, giving rise to the thalamocortical dysrhythmia, proposed to be the mechanism of neurogenic pain as well as other central nervous system (CNS) dysfunctions. Magnetic resonance- and microelectrode-guided stereotactic CL thalamotomy was implemented in 96 patients suffering from chronic therapy-resistant peripheral or central neurogenic pain (mean age: 56 ± 15 years; pain duration before surgery: 7.5 ± 8 years). At a mean follow-up of 3 years, 9 months ± 2 years, 9 months, 53% of the patients benefited from a relief superior to 50% (complete relief in 18.7%). Further analysis of the results demonstrated a significant difference between patients suffering from intermittent as compared with continuous pain. Patients with continuous pain showed only a mean relief of 20.4 ± 25.8% in contrast to the 66 ± 39.2% obtained for patients with intermittent (episodic or paroxysmal) pain manifestations. This was confirmed by the pre- and postoperative visual analogue scale scores showing a significant decrease (59.2%) only in the patient group with intermittent pain. Allodynia was suppressed in 57.3% of the patients. Parameters such as the preoperative pain duration or the site of the causal lesion did not affect the surgical outcome. In 28 patients suffering from unilateral continuous pain, the addition of an ipsilateral CL thalamotomy provided a further significant pain relief. A suppression of drug intake was observed in 31.6% of the patients. Complications occurred in 11.5% of the patients and led to a long term significant disability in only one case. In conclusion, CL thalamotomy is a safe neurosurgical option for neurogenic pain, especially for patients suffering from intermittent pain or allodynia. Its limitation in cases of continuous pain indicates the necessity to explore other stereotactic targets outside of the medial thalamus.