Publications
Concept, neuroanatomy and surgical techniques
The purpose of this study was to describe targeting accuracy in functional neurosurgery using incisionless transcranial magnetic resonance (MR)-guided focused ultrasound technology.
Stereotactic central lateral thalamotomy (CLT) has been applied as a treatment for chronic intractable neuropathic pain. However, it is not clear whether this intervention influences the emotional and cognitive impairments observed in patients who have chronic neuropathic pain.
The object of this study was to describe a method of measuring targeting accuracy in functional neurosurgery using MR imaging and the Stereotactic Atlas of the Human Thalamus and Basal Ganglia. This method should be useful for any functional procedure using these tools or similar ones, and is described here in the specific context of focused ultrasound surgery.
EEG techniques
According to the established pathophysiological concept of Parkinson's disease (PD), the loss of dopaminergic projections from the substantia nigra to the striatum leads to changes in basal ganglia activity (Lozano et al., 1998). The main output from the basal ganglia complex is via the pallido-thalamic tract to the thalamus.
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.
While several mechanisms have been proposed for the pathophysiology of neurogenic pain, no general agreement has been reached yet. In the following we refer to a mechanism that focuses on thalamocortical interplay
Epilepsy, Tinnitus and Neuropsychiatry
After the questionable and inordinately wide application
of the prefrontal lobotomy in the first half of the twentieth century, many groups realized
the necessity of confining surgical interventions to the
paralimbic (or mesocortical) domain. This
gave rise to the three main stereotactic operations still in use
today
The emergence of positive clinical symptoms is viewed as resulting from ectopic gamma-band activation, which we refer to as the "edge effect." This effect is observable as increased coherence between low- and high-frequency oscillations, probably resulting from inhibitory asymmetry between high- and low-frequency thalamocortical modules at the cortical level.
Essential Tremor
Neurogenic Pain
Chronic neuropathic pain may require a neurosurgical treatment, but for reasons that have not been fully explored yet, a significant number of patients do not benefit from the intervention. We compared the resting EEG of 15 healthy controls to the EEG of 23 chronic neuropathic pain patients before and 12 months after treatment by the central lateral thalamotomy (CLT). A patient subgroup had a high (n = 14, pain relief (PR) ≥ 50%) and another subgroup a low (n = 9, PR < 50%) postoperative PR. EEG spectral power and source localization of the high PR patients were normalized postoperatively. In contrast, low PR patients showed postoperative maintenance of insular, cingulate and prefrontal overactivities, and their frustration values were positively correlated with cingulate and prefrontal activity. These findings demonstrate a normalizing effect of CLT on cortical activity and suggest that treatment resistance is associated with a frustration-based dynamics.
During stereotactic functional neurosurgery, stimulation procedure to control for proper target localization provides a unique opportunity to investigate pathophysiological phenomena that cannot be addressed in experimental setups. Here we report on the distribution of response modalities to 487 intraoperative thalamic stimulations performed in 24 neurogenic pain (NP), 17 parkinsonian (PD) and 10 neuropsychiatric (Npsy) patients.
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.
Parkinson
During stereotactic functional neurosurgery, stimulation procedure to control for proper target localization provides a unique opportunity to investigate pathophysiological phenomena that cannot be addressed in experimental setups. Here we report on the distribution of response modalities to 487 intraoperative thalamic stimulations performed in 24 neurogenic pain (NP), 17 parkinsonian (PD) and 10 neuropsychiatric (Npsy) patients.
Oscillatory and coherent EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions. We aimed to study deviations from the norm of different resting EEG parameters in Parkinson's disease (PD) patients. We compared spectral parameters of the resting EEG of PD patients (n=24, median age 67 years) to those of healthy controls (n=34, median age 62 years).
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.