Surgical control of the human thalamocortical dysrhythmia: II. Pallidothalamic tractotomy in Parkinson's disease

Abstract

Following earlier stereotactic experiences, we re-explored the possibilities of a therapeutic lesion of the pallidothalamic tract in the fields HI 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.

High Thalamocortical Theta Coherence in Patients with Parkinson's Disease

“…Selective stereotactic ablation of the pallido-thalamic tract is thought to reduce overinhibition in the thalamus and thereby abolish excessive LTS and EEG theta power during waking, both central elements of TCD. In patients with severe forms of PD resistant to drug treatment, this therapeutic lesion results in ϳ60% improvement of clinical symptoms over the medicated state (Magnin et al, 2001). …”

“…Medication during surgery was aimed at optimal tremor control during recording. The surgical procedure of pallidothalamic tractotomy has been described previously (Magnin et al, 2001). All patients were fully informed about the risks and benefits of the procedure and gave informed consent.…”

“…These nuclei receive projections from the pallido-thalamic tract and are thus affected by the PD pathophysiology. We recorded data from six PD patients during therapeutic intervention (Magnin et al, 2001). The simultaneous recording of scalp EEG with several electrodes allows investigation of both the strength and the topography of the thalamocortical interaction.…”

Subthalamic nucleus stimulation in Parkinson’s disease

“…Pallidothalamic and nigrostriatal fibers coursing immediately dorsal to the STN [54,55] could also be influenced by HFS and could alter the pattern of pallidal output. Pallidofugal tracts have already been the target of ablative neurosurgical interventions [40,70]. Lesions in Forel's field H allow the ablation of both pallidofugal tracts (the ansa lenticularis and the lenticular fasciculus (Forel's field H2), and the ascending projections of the SNr.…”

Cross-modal plasticity in the human thalamus: evidence from intraoperative macrostimulations

“…1b and d) (Magnin et al 2001, Aufenberg et al 2005, Gallay et al, 2008. Primarily indicated against Parkinson's disease, the PTT has also been performed in a small group of neurogenic pain patients presenting a continuous pain 26.11.2009 14 component, often of compressive quality, which tends to resist available procedures including CLT (Jeanmonod et al 2001b).…”