Publications
Concept, neuroanatomy and surgical techniques
The role of the medial thalamus in pain, in particular the intralaminar nuclei, has long been recognized and related to motivational-affective aspects through its afferent connections with the spinothalamic (STT) and spino-reticulothalamic (SRTT) tracts, and efferent projections
to pain-related areas in associative and paralimbic cortical domains. This so-called ‘‘medial pain system’’ has been in the past the target for surgical interventions in patients with chronic, therapy-resistant neuropathic pain.
Anatomical knowledge of the structures to be targeted and of the circuitry involved is crucial in stereotactic functional neurosurgery. The present study was undertaken in the context of surgical treatment of motor disorders such as essential tremor (ET) and Parkinson’s disease (PD) to precisely determine the course and three-dimensional stereotactic localisation of the cerebellothalamic and pallidothalamic tracts in the human brain.
This reference presents a new collection of diagrams of the human thalamus, basal ganglia, and adjoining structures for accurate targeting in stereotactic functional neurosurgery. This guide consists of a series of maps in the three stereotactic planes and comparisons between brains with similar and differing intercommissural distances to help specialists pinpoint precise targets, map through anatomic variations, and develop computerized models for stereotactic functional neurosurgery. Paired with a CD that allows for the enlargement and reader-friendly analysis of maps and illustrations found within the text, this source stands as the first atlas of the human thalamus and basal ganglia to focus on combined high stereotactic precision and anatomical resolution.
EEG techniques
Epilepsy, Tinnitus and Neuropsychiatry
Essential Tremor
Neurogenic Pain
Neurophysiological studies at the cellular level (single unit activity and local field potentials or LFPs) as well as electroencephalographic (EEG) and magnetoencephalographic (MEG) recordings provide converging evidence for a thalamocortical dysregulation at the origin of chronic neurogenic pain of both peripheral and central origin. These data suggest an increase of low frequency thalamocortical rhythmicity originating in disfacilitation of thalamic relay neurons, followed by cortical activation due to asymmetries of corticocortical inhibition. The process, called thalamocortical dysrhythmia (TCD), may become self-sustained and thus chronic, due to recurrent thalamoreticulothalamic and corticoreticulothalamic feedback inhibition.
Functional brain imaging of pain over the last years has provided insight into a distributed anatomical matrix involved in pain processing which includes multiple cortical areas.
Neurophysiological studies at the cellular level (microelectrode unit activity recordings and local field potentials) as well as electro- and magnetoencephalographic recordings provide converging evidence for a thalamocortical dysregulation at the source of chronic neurogenic pain of both peripheral and central origin.
Parkinson
We simultaneously recorded local field potentials (LFP) in the thalamus and EEG on the scalp of 17 patients suffering from neurogenic pain, epilepsy and movement disorders. The EEG of 11 patients displayed enhanced power in the theta frequency range (4–8Hz). The thalamic LFP of 14 patients peaked in the theta range. The theta coherence between EEG and LFP was significant for 12 patients and reached strengths up to 70%. These findings suggest that enhanced theta rhythmicity occurs in tight functional thalamocortical loops and is a major element in all three diseases investigated.
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.
We conclude that the intrinsic oscillatory properties of individual neurons, combined with the dynamic properties of the thalamocortical circuitry, are responsible for the three cardinal parkinsonian symptoms.