Tag: Thalamus

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Multitarget, dual-electrode stimulation for Holmes’ tremor

Multitarget, dual-electrode stimulation for Holmes’ tremor

J Neurosurg 120:1025–1032, 2014

Holmes’ tremor (HT) is generally considered to be a symptomatic tremor associated with lesions of the cerebellum, midbrain, or thalamus. Deep brain stimulation (DBS) therapy for essential tremor and parkinsonian tremor has proved quite successful. In contrast, surgical treatment outcomes for HT have often been disappointing. The use of 2 ipsilateral DBS electrodes implanted in parallel within the thalamus for severe essential tremor has been reported. Since dual-lead stimulation within a single target can cover a wider area than single-lead stimulation, it produces greater effects. On the other hand, DBS of the subthalamic area (SA) was recently reported to be effective for refractory tremor.

Methods. The authors implanted 2 DBS electrodes (one at the nucleus ventralis oralis/nucleus ventralis intermedius and the other at the SA) in 4 patients with HT. For more than 2 years after implantation, each patient’s tremor was evaluated using a tremor rating scale under the following 4 conditions of stimulation: “on” for both thalamus and SA DBS; “off” for both thalamus and SA DBS; “on” for thalamus and “off” for SA DBS; and “on” for SA and “off” for thalamus DBS.

Results. The tremor in all patients was improved for more than 2 years (mean 25.8 ± 3.5 months). Stimulation with 2 electrodes exerted greater effect on the tremor than did 1-electrode stimulation. Interestingly, in all patients progressive effects were observed, and in one patient treated with DBS for 1 year, tremor did not appear even while stimulation was temporarily switched off, suggesting irreversible improvement effects. The presence of both resting and intentional/action tremor implies combined destruction of the pallidothalamic and cerebellothalamic pathways in HT. A larger stimulation area may thus be required for HT patients. Multitarget, dual-lead stimulation permits coverage of the wide area needed to suppress the tremor without adverse effects of stimulation. Some reorganization of the neural network may be involved in the development of HT because the tremor appears several months after the primary insult. The mechanism underlying the absence of tremor while stimulation was temporarily off remains unclear, but the DBS may have normalized the abnormal neural network.

Conclusions. The authors successfully treated patients with severe HT by using dual-electrode DBS over a long period. Such DBS may offer an effective and safe treatment modality for intractable HT.

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Deep Arteriovenous Malformations in the Basal Ganglia, Thalamus, and Insula: Microsurgical Management, Techniques, and Results

Surgery for Deep AVM-1

Neurosurgery 73:417–429, 2013

Arteriovenous malformations (AVMs) in the basal ganglia, thalamus, and insula are considered inoperable given their depth, eloquence, and limited surgical exposure. Although many neurosurgeons opt for radiosurgery or observation, others have challenged the belief that deep AVMs are inoperable. Further discussion of patient selection, technique, and multimodality management is needed.

OBJECTIVE: To describe and discuss the technical considerations of microsurgical resection for deep-seated AVMs.

METHODS: Patients with deep AVMs who underwent surgery during a 14-year period were reviewed through the use of a prospective AVM registry.

RESULTS: Microsurgery was performed in 48 patients with AVMs in the basal ganglia (n = 10), thalamus (n = 13), or insula (n = 25). The most common Spetzler-Martin grade was III2 (68%). Surgical approaches included transsylvian (67%), transcallosal (19%), and transcortical (15%). Complete resection was achieved in 34 patients (71%), and patients with incomplete resection were treated with radiosurgery. Forty-five patients (94%) were improved or unchanged (mean follow-up, 1.6 years).

CONCLUSION: This experience advances the notion that select deep AVMs may be operable lesions. Patients were highly selected for small size, hemorrhagic presentation, young age, and compactness—factors embodied in the Spetzler-Martin and Supplementary grading systems. Overall, 10 different approaches were used, exploiting direct, transcortical corridors created by hemorrhage or maximizing anatomic corridors through subarachnoid spaces and ventricles that minimize brain transgression. The same cautious attitude exercised in selecting patients for surgery was also exercised in deciding extent of resection, opting for incomplete resection and radiosurgery more than with other AVMs to prioritize neurological outcomes.

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Cavernous Malformation of Brainstem, Thalamus, and Basal Ganglia: A Series of 176 Patients

Cavernous_Malformation_of_Brainstem,_Thalamus,_and

Neurosurgery 72:573–589, 2013

Cavernous malformations (CMs) in deep locations account for 9% to 35% of brain malformations and are surgically challenging.

OBJECTIVE: To study the clinical features and outcomes following surgery for deep CMs and the complication of hypertrophic olivary degeneration (HOD).

METHODS: Clinical records, radiological findings, operative details, and complications of 176 patients with deep CMs were reviewed retrospectively.

RESULTS: Of 176 patients with 179 CMs, 136 CMs were in the brainstem, 27 in the basal ganglia, and 16 in the thalamus. Cranial nerve deficits (51.1%), hemiparesis (40.9%), numbness (34.7%), and cerebellar symptoms (38.6%) presented most commonly. Hemorrhage presented in 172 patients (70 single, 102 multiple). The annual retrospective hemorrhage rate was 5.1% (assuming CMs are congenital with uniform hemorrhage risk throughout life); the rebleed rate was 31.5%/patient per year. Surgical approach depended on the proximity of the CM to the pial or ependymal surface. Postoperatively, 121 patients (68.8%) had no new neurological deficits. Follow-up occurred in 170 patients. Delayed postoperative HOD developed in 9/134 (6.7%) patients with brainstem CMs. HOD occurred predominantly following surgery for pontine CMs (9/10 patients). Three patients with HOD had palatal myoclonus, nystagmus, and oscillopsia, whereas 1 patient each had limb tremor and hemiballismus. At follow-up, 105 patients (61.8%) improved, 44 (25.9%) were unchanged, and 19 (11.2%) worsened neurologically. Good preoperative modified Rankin Score (98.2% vs 54.5%, P = .001) and single hemorrhage (89% vs 77.3%, P , .05) were predictive of good longterm outcome.

CONCLUSION: Symptomatic deep CMs can be resected with acceptable morbidity and outcomes. Good preoperative modified Rankin Score and single hemorrhage are predictors of good long-term outcome.

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Dentatorubrothalamic tract in human brain: diffusion tensor tractography study

Neuroradiology (2011) 53:787–791.DOI 10.1007/s00234-011-0878-7
The dentatorubrothalamic tract (DRTT) originates from the dentate nucleus in the cerebellum and terminates in the contralateral ventrolateral nucleus (VL) of the thalamus after decussating to the contralateral red nucleus. Identification of the DRTT is difficult due to the fact that it is a long, multisynaptic, neural tract crossing to the opposite hemisphere. In the current study, we attempted to identify the DRTT in the human brain using a probabilistic tractography technique of diffusion tensor imaging.
Methods Diffusion tensor imaging was performed at 1.5-T using a synergy-L sensitivity encoding head coil. DRTTs were obtained by selection of fibers passing through three regions of interest (the dentate nucleus, the superior cerebellar peduncle, and the contralateral red nucleus) from 41 healthy volunteers. Probabilistic mapping was obtained from the highest probabilistic location at 2.3 mm above the anterior commissure–posterior commissure level.
Results DRTTs of all subjects, which originated from the dentate nucleus, ascended through the junction of the superior cerebellar peduncle and the contralateral red nucleus and then terminated at the VL nucleus of the thalamus. The highest probabilistic location for the DRTT at the thalamus was compatible with the location of the VL nucleus.
Conclusions We identified the DRTT in the human brain using probabilistic tractography. Our results could be useful in research on movement control.

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Dentatorubrothalamic tract in human brain: diffusion tensor tractography study

Neuroradiology(2011)53:787–791.DOI 10.1007/s00234-011-0878-7
The dentatorubrothalamic tract (DRTT) originates  from the dentate nucleus in the cerebellum and terminates in the contralateral ventrolateral nucleus (VL) of the thalamus after decussating to the contralateral red nucleus. Identification of the DRTT is difficult due to the fact that it is a long, multisynaptic, neural tract crossing to the opposite hemisphere.
In the current study, we attempted to identify the DRTT in the human brain using a probabilistic tractography technique of diffusion tensor imaging.
Methods Diffusion tensor imaging was performed at 1.5-T using a synergy-L sensitivity encoding head coil. DRTTs were obtained by selection of fibers passing through three regions of interest (the dentate nucleus, the superior cerebellar peduncle, and the contralateral red nucleus) from 41 healthy volunteers. Probabilistic mapping was obtained from the highest probabilistic location at 2.3 mm above the anterior commissure–posterior commissure level.
Results DRTTs of all subjects, which originated from the dentate nucleus, ascended through the junction of the superior cerebellar peduncle and the contralateral red nucleus and then terminated at the VL nucleus of the thalamus. The highest probabilistic location for the DRTT at the thalamus was compatible with the location of the VL nucleus.
Conclusions We identified the DRTT in the human brain using probabilistic tractography. Our results could be useful in research on movement control.

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Individual Fiber Anatomy of the Subthalamic Region Revealed With Diffusion Tensor Imaging: A Concept to Identify the Deep Brain Stimulation Target for Tremor Suppression

Neurosurgery 68:1069–1076, 2011 DOI: 10.1227/NEU.0b013e31820a1a20

Deep brain stimulation (DBS) has been proven to alleviate tremor of various origins. Distinct regions have been targeted. One explanation for good clinical tremor control might be the involvement of the dentatorubrothalamic tract (DRT) as has been suggested in superficial (thalamic) and inferior (posterior subthalamic) target regions. Beyond a correlation with atlas data and the postmortem evaluation of patients treated with lesion surgery, proof for the involvement of DRT in tremor reduction in the living, the scope of this work, is elusive.

OBJECTIVE: To report a case of unilateral refractory tremor in tremor-dominant Parkinson disease treated with thalamic DBS.

METHODS: Preoperative diffusion tensor imaging (DTI) was performed. Correlation with individual DBS electrode contact locations was obtained through postoperative fusion of helical computed tomography (CT) data with DTI fiber tracking.

RESULTS: Tremor was alleviated effectively. An evaluation of the active electrode contact position revealed clear involvement of the DRT in tremor control. A closer evaluation of clinical effects and side effects revealed a highly detailed individual fiber map of the subthalamic region with DTI fiber tracking.

CONCLUSION: This is the first time the involvement of the DRT in tremor reduction through DBS has been shown in the living. The combination of DTI with postoperative CT and the evaluation of the electrophysiological environment of distinct electrode contacts led to an individual detailed fiber map and might be extrapolated to refined DTI-based targeting strategies in the future. Data acquisition for a larger study group is the topic of our ongoing research.

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Cavernous Malformations of the Brainstem Presenting in Childhood: Surgical Experience in 40 Patients

Neurosurgery 67:1589–1599, 2010 DOI: 10.1227/NEU.0b013e3181f8d1b2

Brainstem cavernous malformations (BSCMs) are believed to compose 9% to 35% of all cerebral cavernous malformations, but these lesions have been reported in children in very limited numbers.

OBJECTIVE: To review surgical outcomes of pediatric patients with BSCMs treated at 1 institution.

METHODS: We retrospectively analyzed the course of 40 pediatric patients (19 males, 21 females; age range, 10 months to 18.9 years; mean, 12.3 years) who underwent surgery between 1984 and 2009. Age, sex, presenting symptoms, location of lesion, surgical approach, new postoperative deficits, Glasgow Outcome Scale score, recurrences, and resolution of baseline symptoms were recorded.

RESULTS: Thirty-nine patients experienced hemorrhage before surgery. Lesion locations included the pons (n = 22), midbrain (n = 4), midbrain and thalamus (n = 4), pontomesencephalic junction (n = 3), medulla (n = 3), pontomedullary junction (n = 3), and cervicomedullary junction (n = 1). Mean lesion size was 2.3 cm. Mean length of hospital stay was 10.7 days. The average clinical follow-up was 31.9 months in 36 patients with follow-up after discharge. At last follow-up, 5 patients had experienced symptoms and/ or imaging consistent with rehemorrhage, either from a residual that enlarged or true recurrence (5.25% annual rebleed risk per patient after surgery); 2 required reoperation for further resection of cavernoma. Mean Glasgow Outcome Scale score was 4.2 on admission, 4.05 at discharge, and 4.5 at latest follow-up. Preoperative symptoms and deficits improved in 16 patients (40%). New neurological deficits developed in 19 patients (48%) and resolved in 9, leaving 10 patients (25%) with new permanent deficit.

CONCLUSION: Compared with adults, pediatric patients with BCSMs tend to have larger lesions and higher rates of recurrence (regrowth of residual lesion). Given the greater life expectancy of children, surgical treatment seems warranted in those with surgically accessible lesions that have bled. Outcomes were similar to those in our adult series of patients with BSCMs.

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An Assessment of Current Brain Targets for Deep Brain Stimulation Surgery With Susceptibility- Weighted Imaging at 7 Tesla

Neurosurgery 67:1745–1756, 2010 DOI: 10.1227/NEU.0b013e3181f74105

Deep brain stimulation (DBS) surgery is used for treating movement disorders, including Parkinson disease, essential tremor, and dystonia. Successful DBS surgery is critically dependent on precise placement of DBS electrodes into target structures. Frequently, DBS surgery relies on normalized atlas-derived diagrams that are superimposed on patient brain magnetic resonance imaging (MRI) scans, followed by microelectrode recording and macrostimulation to refine the ultimate electrode position. Microelectrode recording carries a risk of hemorrhage and requires active patient participation during surgery.

OBJECTIVE: To enhance anatomic imaging for DBS surgery using high-field MRI with the ultimate goal of improving the accuracy of anatomic target selection.

METHODS: Using a 7-T MRI scanner combined with an array of acquisition schemes using multiple image contrasts, we obtained high-resolution images of human deep nuclei in healthy subjects.

RESULTS: Superior image resolution and contrast obtained at 7 T in vivo using susceptibility-weighted imaging dramatically improved anatomic delineation of DBS targets and allowed the identification of internal architecture within these targets. A patient-specific, 3-dimensional model of each target area was generated on the basis of the acquired images.

CONCLUSION: Technical developments in MRI at 7 T have yielded improved anatomic resolution of deep brain structures, thereby holding the promise of improving anatomicbased targeting for DBS surgery. Future study is needed to validate this technique in improving the accuracy of targeting in DBS surgery.

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