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Biomedical subjects

Adnan Koudsie

Publications and source records attributed to Adnan Koudsie.

7 recordsLinked to original sources
PubMed2006

Pretargeting for the implantation of stimulation electrodes into the subthalamic nucleus: a comparative study of magnetic resonance imaging and ventriculography.

OBJECTIVE: The optimal imaging modality for preoperative targeting of the subthalamic nucleus (STN) for high-frequency stimulation is controversially discussed. Commonly used methods were stereotactic magnetic resonance imaging (MRI), stereotactic ventriculography, and fusion between MRI and stereotactic computer tomography. All of these techniques not only have their own advantages but also specific limitations and drawbacks. The purpose of this study was to evaluate the accuracy of the preoperative MRI targeting as compared with ventriculography in terms of both the STN target as well as the internal landmarks. METHODS: Thirty patients with Parkinson's disease who underwent bilateral surgery for STN-high-frequency stimulation received both stereotactic ventriculography and stereotactic MRI. The theoretical target was determined by each of these two imaging modalities. The final electrode placement was performed after extensive electrophysiological evaluation using microrecording and microstimulation. The real target was assumed to be given by the electrode contact with the best clinical result assessed by the United Parkinson's Disease Rating Scale in the postoperative follow-up. In addition, the coordinates of the two landmarks, anterior commissure and posterior commissure, were determined using both imaging methods. RESULTS: The mean targeting error was 4.1 +/- 1.7 mm (mean +/- standard deviation) for MRI and 2.4 +/- 1.1 mm for ventriculography (P < 0.0001). The mean target mismatch between the two imaging methods was 2.9 +/- 1.2 mm. The length of the anterior commissure-posterior commissure distance differed significantly (P < 0.0001) between MRI (27.6 +/- 1.6 mm) and ventriculography (25.0 +/- 1.3 mm). The mismatch was mainly induced by an anterior diplacement of the anterior commissure by 1.9 +/- 2.2 mm (P < 0.0001) in MRI determination, as compared with ventriculography. CONCLUSION: Our findings show that the indirect targeting of the STN using coordinates based on radiological landmarks is more accurate than the direct targeting using anatomic visualization of the target structure. Regardless of the imaging procedure, electrophysiological mapping is required for optimal electrode placement, although in 20% of cases, the target determined by MRI falls out of the radius explored by electrophysiology.

Brain Mapping↗
PubMed2003

Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease.

BACKGROUND: Although the short-term benefits of bilateral stimulation of the subthalamic nucleus in patients with advanced Parkinson's disease have been well documented, the long-term outcomes of the procedure are unknown. METHODS: We conducted a five-year prospective study of the first 49 consecutive patients whom we treated with bilateral stimulation of the subthalamic nucleus. Patients were assessed at one, three, and five years with levodopa (on medication) and without levodopa (off medication), with use of the Unified Parkinson's Disease Rating Scale. Seven patients did not complete the study: three died, and four were lost to follow-up. RESULTS: As compared with base line, the patients' scores at five years for motor function while off medication improved by 54 percent (P<0.001) and those for activities of daily living improved by 49 percent (P<0.001). Speech was the only motor function for which off-medication scores did not improve. The scores for motor function on medication did not improve one year after surgery, except for the dyskinesia scores. On-medication akinesia, speech, postural stability, and freezing of gait worsened between year 1 and year 5 (P<0.001 for all comparisons). At five years, the dose of dopaminergic treatment and the duration and severity of levodopa-induced dyskinesia were reduced, as compared with base line (P<0.001 for each comparison). The average scores for cognitive performance remained unchanged, but dementia developed in three patients after three years. Mean depression scores remained unchanged. Severe adverse events included a large intracerebral hemorrhage in one patient. One patient committed suicide. CONCLUSIONS: Patients with advanced Parkinson's disease who were treated with bilateral stimulation of the subthalamic nucleus had marked improvements over five years in motor function while off medication and in dyskinesia while on medication. There was no control group, but worsening of akinesia, speech, postural stability, freezing of gait, and cognitive function between the first and the fifth year is consistent with the natural history of Parkinson's disease.

Activities of Daily Living↗
PubMed2002

Treatment results: Parkinson's disease.

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.

Electric Stimulation Therapy↗
PubMed2002

Imaging of subthalamic nucleus and ventralis intermedius of the thalamus.

The techniques of targeting the subthalamic nucleus (STN) and the ventralis intermedius nucleus (Vim) are similar, only the coordinates are different. Targeting ideally consists of gathering all data about a target and positioning the electrode correctly within that target. The electrode should be positioned within a statistical range of coordinates, where the neuronal firing fits a given pattern and responds to external stimuli, particularly to proprioceptive inputs, in a somatotopically organized manner. Moreover, final placement should provide the best clinical improvement of symptoms under the stimulation parameters expected to be used in the long term. This latter criterion is by far the most important, because intraoperative findings indicate the functional benefit for the patient, which is the ultimate purpose of this surgery. A variety of radiological modalities are available to provide data for electrode placement, but each type has its drawbacks. Ventriculography, although safe when performed accordingly to strict technical procedure, is the most precise method but provides more indirect targeting and is more invasive than magnetic resonance imaging (MRI). MRI is the best method for visualizing the STN and, to some extent, for discerning the Vim, but it is plagued with unpredictable and nonreproducible deformations that induce a systematic distortion. These shortcomings no doubt will be corrected in the near future, and the technologies will better assist us in the proper placement of electrodes, which will provide the patient with the highest possible benefit.

Cerebral Ventriculography↗
PubMed2002

Intraoperative microrecordings of the subthalamic nucleus in Parkinson's disease.

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.

Brain Mapping↗
PubMed2002

Deep brain stimulation in epilepsy with particular reference to the subthalamic nucleus.

Alternative methods, for the treatment of medically refractory epileptic patients, who cannot be treated by resective surgery, such as chronic deep brain neurostimulation, are under development. Such methods have been used in the cerebellum, various thalamic nuclei, and in the caudate nucleus. In Grenoble, encouraged by the suppressive effects of pharmacological or electrical inhibition of the STN on different types of seizure in animal models of epilepsy, and by our experience with STN high frequency stimulation (HFS) in patients with movement disorders, we have evaluated the high frequency stimulation of the subthalamic nucleus (STN HFS). STN HFS was performed in five patients suffering from medically intractable seizures and considered unsuitable for resective surgery. A 67% to 80% reduction in seizure frequency was observed in three patients, with a partial symptomatic epilepsy of the central region. An additional patient suffering from severe myoclonic epilepsy (Dravet syndrome) also responded to STN HFS, with a weaker reduction of seizure frequency. The fifth patient who suffered from an autosomal dominant frontal lobe epilepsy with insulo-frontal seizures did not show any improvement. These results suggest that stimulation of STN could be a promising treatment for patients with drug-resistant epilepsy who would not benefit from conventional surgery.

Adolescent↗