Thalamic anterior part of the ventral posterolateral nucleus and central lateral nucleus in the genesis of central post-stroke pain.

BACKGROUND: The genesis of central post-stroke pain (CPSP) is important but difficult to understand. We evaluated the involvement of the thalamic anterior part of the ventral posterolateral nucleus (VPLa) and central lateral nucleus (CL) in the occurrence of CPSP. METHOD: Stereotactic thalamotomy was performed on the posterior part of the ventral lateral nucleus (VLp)-VPLa and CL in 9 patients with CPSP caused by deep-seated intracerebral hemorrhage. Computed tomography (CT) did not reveal definite thalamic lesion in 5 patients but did in 4 patients. Electrophysiological studies of these thalamic nuclei were carried out during the surgery. Anatomical studies using CT were performed in another 20 patients with thalamic hemorrhage who had clear consciousness but had sensory disturbance at onset. RESULTS: Neural activities were preserved and hyperactive and unstable discharges (HUDs) were often recognized along the trajectory in the thalamic VLp-VPLa in 5 patients without thalamic lesion. Surgical modification of this area ameliorated pain, particularly movement-related pain. Neural activities were hypoactive in the other 4 patients with thalamic lesion. However, neural activities were preserved and HUDs were sometimes recognized in the CL. Sensory responses were seen, but at low rate, in the sensory thalamus. Anatomical study showed that the thalamic lesion was obviously smaller in the patients with developing pain in the chronic stage. CONCLUSIONS: Change in neural activities around the cerebrovascular disease lesion in the thalamic VPLa or CL might affect the perception of sensory impulses or sensory processing in those thalamic nuclei, resulting in the genesis of CPSP.

Electrical Thalamic Stimulation in the Anterior Part of the Ventral Posterolateral Nucleus for the Treatment of Patients With Central Poststroke Pain.

OBJECTIVES: The effects of thalamic stimulation of the anterior part of the ventral posterolateral nucleus (VPLa) for central poststroke pain (CPSP) and the pain-related electrophysiological characteristics of this structure were investigated. MATERIALS AND METHODS: Nine patients with CPSP manifesting as hemibody pain were enrolled. Stereotactic thalamic VPLa stimulation was implemented, and intraoperative electrophysiological studies on hyperactive and unstable discharges (HUDs) and responses to sensory and electrical stimulation were performed in the sensory thalamus. A preoperative somatosensory-evoked potential (SEP) study was carried out in all nine patients and in eight other patients with localized pain. RESULTS: The patients were classified into two groups: a HUD-dominant group (group H, n = 5) and a sensory response-dominant group (group R, n = 4). HUDs were frequently encountered in the thalamic VPLa in the former group. The total number of HUDs and the number along the trajectory to the VPLa in group H were significantly larger than those in group R. The improvements on the pain numeric rating scale in group H were significantly higher than those in group R two years after surgery. The amplitude ratio of the SEP N20s in the ipsilateral to the contralateral side of CVD lesion in the study group was significantly lower than in the localized pain group. CONCLUSIONS: Adequate and stable pain relief with thalamic VPLa stimulation is obtainable in patients with CPSP who exhibit hyperactivity and electrical instability along the trajectory to this nucleus. Both responders and nonresponders were found to have severe dysfunction of the lemniscal system.

Stereotactic Selective Thalamotomy for Focal Dystonia with Aid of Depth Microrecording.

OBJECTIVE: Long-term effectiveness of selective ventralis intermedius nucleus (VIM)-ventralis oralis nucleus (VO) thalamotomy with depth microrecording for the treatment of focal dystonia was evaluated. The optimal thalamic areas for controlling focal dystonia were studied based on the electrophysiologic and anatomic data. METHODS: Stereotactic selective VIM-VO thalamotomy with depth microrecording was carried out in 8 patients with focal arm and hand dystonia and in 1 patient with cervical dystonia. Electrophysiologic data on the lateral part of thalamic VIM were studied in patients with focal dystonia. A very small and narrow therapeutic lesion was formed in the shape of a square on the sagittal plane and of an I, rotated V, Y, or inverse Y on the axial plane in the VIM-VO, which covered the kinesthetic response area topographically related to focal dystonia. Patients with arm and hand dystonia were followed up for 4.7 ± 3.0 years and 1 patient with cervical dystonia was followed up for 18.2 years. RESULTS: Marked improvement of focal dystonia was shown by functional assessment using the Unified Dystonia Rating Scale. Transient dysarthria was recognized in 1 patient. The sequence of body localization of kinesthetic response in the VIM was clearly shown in patients with focal dystonia. Decreases in the amplitude and amplitude ratio of electromyography on the forearm muscles were markedly significant after VIM thalamotomy, but insignificant after VO thalamotomy immediately after VIM thalamotomy. CONCLUSIONS: Marked reduction of electromyographic tonic discharges of focal dystonia was shown after VIM lesioning. Selective VIM-VO thalamotomy showed good and long-term stable effects for focal dystonia.

Superselective Thalamotomy in the Most Lateral Part of the Ventralis Intermedius Nucleus for Controlling Essential and Parkinsonian Tremor.

OBJECTIVE: The minimum and essential thalamic areas for reducing tremor were investigated in cases treated by superselective thalamotomy in the most lateral part of the ventralis intermedius nucleus (mlp-VIM). METHODS: Stereotactic superselective VIM thalamotomy with depth microrecording was performed in 21 patients with essential tremor (ET) and 15 patients with tremor-dominant Parkinson disease (PD). A very small and narrow (axial plane) therapeutic lesion was formed as a square on the sagittal plane and inverse V on the axial plane in the mlp-VIM, which covered the kinesthetic response area topographically related to tremor. Patients with ET were followed up for 4.7 ± 3.0 years and patients with PD for 7.9 ± 3.9 years. RESULTS: Almost complete tremor control was achieved in all patients immediately after surgery and continued for up to 8 years. A few adverse events were recognized but disappeared within 1 month without 1 patient with thalamic hemorrhage. The medial border of the therapeutic lesion was significantly more lateral in both patients with ET and patients with PD than the calculated standard target point and was in patients with PD than in patients with ET. The mean width was only about 2.4 mm. The individual differences of the adequate location of the therapeutic lesion were significantly greater in the ET than in the PD group. CONCLUSIONS: The important area for reducing tremor was small and narrow and was located in the mlp-VIM, where the proprioceptive ascending signals from the tremor-dominant body part are conducted. Superselective thalamotomy in the mlp-VIM was safe and effective for the long-term in patients with ET and PD.

Transduction Profile of the Marmoset Central Nervous System Using Adeno-Associated Virus Serotype 9 Vectors.

The common marmoset is a small New World primate that has attracted remarkable attention as a potential experimental animal link between rodents and humans. Adeno-associated virus (AAV) vector-mediated expression of a disease-causing gene or a potential therapeutic gene in the brain may allow the construction of a marmoset model of a brain disorder or an exploration of the possibility of gene therapy. To gain more insights into AAV vector-mediated transduction profiles in the marmoset central nervous system (CNS), we delivered AAV serotype 9 (AAV9) vectors expressing GFP to the cisterna magna or the cerebellar cortex. Intracisternally injected AAV9 vectors expanded in the CNS according to the cerebrospinal fluid (CSF) flow, by retrograde transport through neuronal axons or via intermediary transcytosis, resulting in diffuse and global transduction within the CNS. In contrast, cerebellar parenchymal injection intensely transduced a more limited area, including the cerebellar cortex and cerebellar afferents, such as neurons of the pontine nuclei, vestibular nucleus and inferior olivary nucleus. In the spinal cord, both administration routes resulted in labeling of the dorsal column and spinocerebellar tracts, presumably by retrograde transport from the medulla oblongata and cerebellum, respectively. Motor neurons and dorsal root ganglia were also transduced, possibly by diffusion of the vector down the subarachnoid space along the cord. Thus, these two administration routes led to distinct transduction patterns in the marmoset CNS, which could be utilized to generate different disease animal models and to deliver therapeutic genes for the treatment of diseases affecting distinct brain areas.

Resection extent of the supplementary motor area and post-operative neurological deficits in glioma surgery.

Objective The supplementary motor area (SMA) is important for the prediction of post-operative symptoms after surgical resection of gliomas. We investigated the relationships between clinical factors and the resection range of SMA gliomas, and the post-operative neurological symptoms. Methods We retrospectively studied 18 consecutive surgeries for gliomas involving the SMA proper performed in 13 patients. Seven cases were recurrence of the tumour. Clinical factors and details of specific resection of the SMA proper (resection of posterior part, medial wall) and cingulate motor area (CMA) were examined. Results Eight cases suffered new post-operative neurological deficits. Six of these eight cases had transient deficits. Permanent deficits persisted in two cases with partial weakness or paresis, after rapid improvement of post-operative global weakness or hemiplegia, respectively. The risk of post-operative neurological deficits was not associated with the resection of the posterior part of the SMA proper or the CMA, but was associated with resection of the medial wall of the SMA proper. Surgery for recurrent tumour was associated with post-operative neurological deficits. The medial wall was frequently resected in recurrent cases. Discussion The frequency of post-operative neurological symptoms, including SMA syndrome, may be higher after resection of the medial wall of the SMA proper compared with the resection of only the lateral surface of the SMA proper.

Microrecording and image-guided stereotactic biopsy of deep-seated brain tumors.

OBJECT: Image-guided stereotactic brain tumor biopsy cannot easily obtain samples of small deep-seated tumor or selectively sample the most viable region of malignant tumor. Image-guided stereotactic biopsy in combination with depth microrecording was evaluated to solve such problems. METHODS: Operative records, MRI findings, and pathological specimens were evaluated in 12 patients with small deep-seated brain tumor, in which image-guided stereotactic biopsy was performed with the aid of depth microrecording. The tumors were located in the caudate nucleus (1 patient), thalamus (7 patients), midbrain (2 patients), and cortex (2 patients). Surgery was performed with a frameless stereotactic system in 3 patients and with a frame-based stereotactic system in 9 patients. Microrecording was performed to study the electrical activities along the trajectory in the deep brain structures and the tumor. The correlations were studied between the electrophysiological, MRI, and pathological findings. Thirty-two patients with surface or large brain tumor were also studied, in whom image-guided stereotactic biopsy without microrecording was performed. RESULTS: The diagnostic yield in the group with microrecording was 100% (low-grade glioma 4, high-grade glioma 4, diffuse large B-cell lymphoma 3, and germinoma 1), which was comparable to 93.8% in the group without microrecording. The postoperative complication rate was as low as that of the conventional image-guided method without using microelectrode recording, and the mortality rate was 0%, although the target lesions were small and deep-seated in all cases. Depth microrecording revealed disappearance of neural activity in the tumor regardless of the tumor type. Neural activity began to decrease from 6.3 ± 4.5 mm (mean ± SD) above the point of complete disappearance along the trajectory. Burst discharges were observed in 6 of the 12 cases, from 3 ± 1.4 mm above the point of decrease of neural activity. Injury discharges were often found at 0.5-1 mm along the trajectory between the area of decreased and disappeared neural activity. Close correlations between electrophysiological, MRI, and histological findings could be found in some cases. CONCLUSIONS: Image-guided stereotactic biopsy performed using depth microrecording was safe, it provided accurate positional information in real time, and it could distinguish the tumor from brain structures during surgery. Moreover, this technique has potential for studying the epileptogenicity of the brain tumor.

Effect of ventralis intermedius thalamotomy on the area in the sensorimotor cortex activated by passive hand movements: fMR imaging study.

Stereotactic ventralis intermedius (Vim) thalamotomy is effective for essential tremor (ET) of the limb, but the effect on the activity of the sensorimotor cortex is still unclear. The functional changes in this cortical area of patients with ET after Vim thalamotomy were investigated using functional magnetic resonance (fMR) imaging. Six patients underwent Vim thalamotomy for medically intractable ET, predominantly in the right hand. 1.5-tesla fMR imaging was performed using the blood oxygenation level-dependent sequence, before and after Vim thalamotomy, during passive movements with right wrist flexion and extension. Before and after images were analyzed using SPM99 software. Activation in the sensorimotor cortex and supplementary motor area evoked by wrist passive movement was observed both before and after surgery. Group analysis of changes in the blood oxygenation level-dependent response revealed a significantly smaller activated area postoperatively. Activation at the fundus of the central sulcus was characteristically decreased. All patients showed marked improvement in tremor after Vim thalamotomy. No patient experienced neurological deficits. fMR imaging showed that activation at the fundus of the central sulcus evoked by passive wrist movement was suppressed after Vim thalamotomy in ET patients, probably due to disruption of the thalamocortical pathway. The fundus of the central sulcus (Brodmann area 3a) is likely to be one of the key relays in the tremor circuit.

Transcranial electrical stimulation through screw electrodes for intraoperative monitoring of motor evoked potentials. Technical note.

The feasibility of high-frequency transcranial electrical stimulation (TES) through screw electrodes placed in the skull was investigated for use in intraoperative monitoring of the motor pathways in patients who are in a state of general anesthesia during cerebral and spinal operations. Motor evoked potentials (MEPs) were elicited by TES with a train of five square-wave pulses (duration 400 microsec, intensity < or = 200 mA, frequency 500 Hz) delivered through metal screw electrodes placed in the outer table of the skull over the primary motor cortex in 42 patients. Myogenic MEPs to anodal stimulation were recorded from the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. The mean threshold stimulation intensity was 48 +/- 17 mA for the APB muscles, and 112 +/- 35 mA for the TA muscles. The electrodes were firmly fixed at the site and were not dislodged by surgical manipulation throughout the operation. No adverse reactions attributable to the TES were observed. Passing current through the screw electrodes stimulates the motor cortex more effectively than conventional methods of TES. The method is safe and inexpensive, and it is convenient for intraoperative monitoring of motor pathways.

Reliable and convenient method for the fixation of recording electrodes on nonshaved scalp for intraoperative electrophysiological monitoring: technical note.

BACKGROUND: Difficulties with the intraoperative monitoring of evoked responses sometimes occur because of displacement or dislodgment of the recording electrodes during surgery, especially if placed on nonshaved scalp. METHODS: An alternative fixation method of the recording electrode on the nonshaved scalp was developed. The sterile subdermal needle electrode was attached on the scalp by application of a transparent dressing (Tegaderm) over the electrode followed by fixing with a skin stapler. RESULTS: The needle electrodes were easily, quickly, and firmly positioned even on the nonshaved scalp. The responses of the intraoperative evoked potentials were highly stable and reproducible throughout the operation. CONCLUSION: This fixation method for subdermal needle electrodes on the scalp is safe, reliable, and convenient for intraoperative electrophysiological monitoring of evoked potentials, even if the scalp is not shaved.