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Jamal M. Taha, Jacques Favre, Thomas K. Baumann and Kim J. Burchiel

✓ The goals of this study were to analyze the effect of pallidotomy on parkinsonian tremor and to ascertain whether an association exists between microrecording findings and tremor outcome.

Forty-four patients with Parkinson's disease who had drug-induced dyskinesia, bradykinesia, rigidity, and tremor underwent posteroventral pallidotomy. Using a 1-µ-tip tungsten electrode, microrecordings were obtained through one to three tracts, starting 10 mm above the pallidal base. Tremor severity was measured on a patient-rated, 100-mm Visual Analog Scale (VAS), both preoperatively and 3 to 9 months (mean 6 months) postoperatively.

Preoperatively, tremor was rated as 50 mm or greater in 24 patients (55%) and as less than 25 mm in 13 patients (30%). Postoperatively, tremor was rated as 50 mm or greater in five patients (11%) and less than 25 mm in 29 patients (66%). The difference was significant (p = 0.0001). Four patients (9%) had no postoperative tremor. Tremor improved by at least 50% in eight (80%) of 10 patients in whom tremor-synchronous cells were recorded (Group A) and in 12 (35%) of 34 patients in whom tremor-synchronous cells were not recorded (Group B). This difference was significant (p = 0.03). Tremor improved by at least 50 mm in all (100%) of the seven Group A patients with severe (≥ 50 mm) preoperative tremor and in nine (53%) of 17 Group B patients with severe preoperative tremor. This difference was also significant (p = 0.05).

The authors proffer two conclusions: 1) after pallidotomy, tremor improves by at least 50% in two-thirds of patients with Parkinson's disease who have severe (≥ 50 mm on the VAS) preoperative tremor; and 2) better tremor control is obtained when tremor-synchronous cells are included in the lesion.

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Jamal M. Taha, Jacques Favre, Thomas K. Baumann and Kim J. Burchiel

The goals of this study were to analyze the effect of pallidotomy on parkinsonian tremor and to ascertain whether an association exists between microrecording findings and tremor outcome.

Forty-four patients with Parkinson's disease (PD) who had drug-induced dyskinesia, bradykinesia, rigidity, and tremor underwent posteroventral pallidotomy. Using a 1-μ-tip tungsten electrode, microrecordings were obtained through one to three tracts, starting 10 mm above the pallidal base. Tremor severity was measured on a patient-rated, 100-mm Visual Analog Scale (VAS), both preoperatively and 3 to 9 months (mean 6 months) postoperatively.

Preoperatively, tremor was rated as 50 mm or greater in 24 patients (55%) and as less than 25 mm in 13 patients (30%). Postoperatively, tremor was rated as 50 mm or greater in five patients (11%) and less than 25 mm in 29 patients (66%). The difference was significant (p = 0.0001). Four patients (9%) had no postoperative tremor. Tremor improved by at least 50% in eight (80%) of 10 patients in whom tremor-synchronous cells were recorded (Group A) and in 12 (35%) of 34 patients in whom tremor-synchronous cells were not recorded (Group B). This difference was significant (p = 0.03). Tremor improved by at least 50 mm in all (100%) of the seven Group A patients with severe (>= 50 mm) preoperative tremor and in nine (53%) of 17 Group B patients with severe preoperative tremor. This difference was also significant (p = 0.05).

The authors proffer two conclusions: 1) after pallidotomy, tremor improves by at least 50% in two-thirds of patients with PD who have severe (>= 50 mm on the VAS) preoperative tremor; and 2) better tremor control is obtained when tremor-synchronous cells are included in the lesion.

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Jamal M. Taha, Jacques Favre, Thomas K. Baumann and Kim J. Burchiel

✓ Information is limited on the characteristics and topographic localization of pallidal kinesthetic cells in patients with Parkinson's disease. The authors analyzed the data from 298 neurons recorded in 38 patients with Parkinson's disease who underwent pallidotomy via microrecording techniques. Sixty-five neurons (22%) responded to passive movement of contralateral limbs. Of 17 kinesthetic cells that were tested in six patients, seven (41%) responded to ipsilateral limb movement as well. Nineteen cells (6%) fired synchronously with tremor. More kinesthetic cells were activated (63%) than inhibited (28%) by movement of single (68%) rather than multiple (32%) joints, and proximal (75%) rather than distal (25%) joints. The lateral globus pallidus externus (GPe) and medial globus pallidus internus (GPi) pallidal segments contained similar proportions of kinesthetic cells, activated or inhibited cells, arm- or leg-activated cells, and cells responding to single or multiple joints. Significantly more kinesthetic cells that responded to distal joints were recorded in GPi compared to GPe segments (p = 0.01). Arm and leg cells had similar characteristics pertaining to activation versus inhibition and responses to single, multiple, proximal, or distal joint movements. Arm and leg cells were somatotopically organized in GPi. Arm cells were clustered at the rostral and caudal segments of GPi and leg cells were clustered centrally. In GPe, leg cells were clustered at the caudal border. No somatotopic organization was identified for activated or inhibited cells; cells that responded to single, multiple, proximal, or distal joints; tremor-synchronous cells; or cells responding to specific joints within somatotopic arm or leg cells. It is concluded that kinesthetic cells provide a roadmap that localizes limb cells during pallidotomy. More studies are needed to identify the clinical significance of the different characteristics of kinesthetic cells.

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Laura Rocchi, Patricia Carlson-Kuhta, Lorenzo Chiari, Kim J. Burchiel, Penelope Hogarth and Fay B. Horak

Object

Difficulty with step initiation, called “start hesitation,” is related to gait bradykinesia and is an early hallmark of gait freezing in Parkinson disease (PD). Authors of this study investigated the effects of deep brain stimulation (DBS) and levodopa on step initiation before and 6 months after DBS surgery in 29 patients with PD who were randomized to either the bilateral subthalamic nucleus (STN) or globus pallidus internus (GPi) as the DBS site.

Methods

The authors measured the amplitude and duration of anticipatory postural adjustments (APAs), the feed-forward postural preparation that precedes the onset of voluntary step initiation, based on center-of-pressure displacements on a force plate. They also measured the length and velocity of the first step using a motion analysis system to study kinematics. Some of the patients (22) were from a large, multicenter, double-blind clinical trial, and all patients in the study (29, PD-DBS group) were randomized to DBS in either the bilateral STN (15 patients) or bilateral GPi (14 patients). Differences in step initiation were investigated in 2 conditions before surgery (off/on levodopa) and in 4 conditions after surgery (off/on levodopa combined with off/on DBS). Twenty-eight elderly healthy control volunteers (CTRL group) were also tested, and 9 control volunteers with PD who met the criteria for DBS (PD-C group) were tested at baseline and 6 months later.

Results

Patients in the PD-DBS group had smaller amplitudes and longer durations of APAs compared with those in the 28 healthy control volunteers in all conditions. Before surgery, APAs improved with levodopa. After surgery, the APAs were significantly worse than in the best-treatment state before surgery (DOPA condition), and responsiveness to levodopa decreased. No differences in APAs were detected between the STN and GPi groups. A comparison with PD control volunteers who did not undergo DBS surgery confirmed that a deterioration in step preparation was not related to disease progression.

Step length and velocity were smaller in the PD-DBS group than in controls in all conditions. Before surgery, levodopa improved the length and velocity of the first step. Both step length and velocity were unchanged in the best-treatment state before surgery (DOPA condition) as compared with after surgery (DBS+DOPA), with only step velocity in the STN group getting worse after surgery.

Conclusions

Six months of DBS in the STN or GPi impaired anticipatory postural preparation for step initiation, the opposite effect as with levodopa. Deep brain stimulation disrupted postural preparation more than step execution, suggesting independent motor pathways for preparation and execution of gait. Although turning the stimulators on after surgery combined with levodopa benefited the postural preparation to step, a comparison of pre- and postsurgery conditions suggests that either the surgery itself or 6 months of continuous stimulation may lead to an alteration of circuits or plastic changes that impair step initiation.

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Ahmed M. Raslan, Reynaldo DeJesus, Caglar Berk, Andrew Zacest, Jim C. Anderson and Kim J. Burchiel

Object

Hemifacial spasm is a clinical syndrome caused by vascular compression of the facial nerve in the cerebellopontine angle, which can be relieved by surgical intervention. Advances in medical imaging technology allow for direct visualization of the offending blood vessels in hemifacial spasm and similar conditions (such as trigeminal neuralgia). The utility of high resolution 3D MR angiography and 3D spoiled-gradient recalled (SPGR) imaging sequences for surgical decision-making in hemifacial spasm, as measured by sensitivity, specificity, and positive and negative predictive values, has not been previously determined.

Methods

A retrospective review was undertaken of 23 patients with hemifacial spasm who underwent operations between January 2001 and December 2006 at Oregon Health & Science University. All patients underwent preoperative high-resolution 3D MR angiography and 3D SPGR imaging. The sensitivity of the SPGR imaging/MR angiography interpretation of neurovascular compression (NVC) by both a neurosurgeon and 2 neuroradiologists was determined in relation to the presence of actual NVC during surgery.

Results

All patients were found to have NVC at surgery. After review by a neurosurgeon and 2 neuroradiologists, imaging data from 19 of the 23 patients were evaluated. The neurosurgeon's interpretation had a sensitivity of 79% and a positive predictive value (PPV) of 100%. The first neuroradiologist's interpretation had a sensitivity of 21% with a PPV of 100%. Further interpretation by a blinded second neuroradiologist with expertise in MR imaging of hemifacial spasm and trigeminal neuralgia was conducted, and sensitivity was 59% and PPV was 100%. Specificity was not determined because there were no true negative cases. The negative predictive value was 0% for both the neurosurgeon's and neuroradiologists' evaluations.

Conclusions

Although high-resolution 3D MR angiography and 3D SPGR imaging was helpful in providing information about the anatomical relationship of cranial nerve VII and surrounding blood vessels, the authors determined that in the case of hemifacial spasm these types of imaging did not influence preoperative surgical decisionmaking.

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Jonathan P. Miller, Stephen T. Magill, Feridun Acar and Kim J. Burchiel

Object

Microvascular decompression (MVD) is an effective treatment for trigeminal neuralgia (TN). However, many patients do not experience complete pain relief, and relapse can occur even after an initial excellent result. This study was designed to identify characteristics associated with improved long-term outcome after MVD.

Methods

One hundred seventy-nine consecutive patients who had undergone MVD for TN at the authors' institution were contacted, and 95 were enrolled in the study. Patients provided information about preoperative pain characteristics including preponderance of shock-like (Type 1 TN) or constant (Type 2 TN) pain, preoperative duration, trigger points, anticonvulsant therapy response, memorable onset, and pain-free intervals. Three groups were defined based on outcome: 1) excellent, pain relief without medication; 2) good, mild or intermittent pain controlled with low-dose medication; and 3) poor, severe persistent pain or need for additional surgical treatment.

Results

Type of TN pain (Type 1 TN vs Type 2 TN) was the only significant predictor of outcome after MVD. Results were excellent, good, and poor for Type 1 TN versus Type 2 TN patients in 60 versus 25%, 24 versus 39%, and 16 versus 36%, respectively. Among patients with each TN type, there was a significant trend toward better outcome with greater proportional contribution of Type 1 TN (lancinating) symptoms (p < 0.05).

Conclusions

Pain relief after MVD is strongly correlated with the lancinating pain component, and therefore type of TN pain is the best predictor of long-term outcome after MVD. Application of this information should be helpful in the selection of TN patients likely to benefit from MVD.

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Konstantin V. Slavin, Randall R. Nixon, Gary M. Nesbit and Kim J. Burchiel

The authors present the case of a patient in whom progressive thoracic myelopathy was caused by the extensive ossification of the arachnoid membrane and associated intramedullary syrinx. Based on their findings and the results of a literature search, they describe a pathological basis of this rare condition, discuss its incidence and symptomatology, and suggest a simple classification of various types of the arachnoid ossification. They also discuss magnetic resonance imaging features of arachnoid ossification and associated spinal cord changes. Emphasis is placed on the particular value of plain computerized tomography, which is highly sensitive for detecting intraspinal calcifications and ossifications, in the diagnostic evaluation of patients whose clinical picture indicates progressive myelopathy.

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Konstantin V. Slavin, Randall R. Nixon, Gary M. Nesbit and Kim J. Burchiel

✓ The authors present the case of progressive thoracic myelopathy caused by the extensive ossification of the arachnoid membrane and associated intramedullary syrinx. Based on their findings and results of the literature search, they describe a pathological basis for this rare condition, discuss its incidence and symptomatology, and suggest a simple classification for various types of the arachnoid ossification. They also discuss the magnetic resonance imaging features of arachnoid ossification and associated spinal cord changes. The particular value of plain computerized tomography, which is highly sensitive in revealing intraspinal calcifications and ossifications, in the diagnostic evaluation of patients with a clinical picture of progressive myelopathy is emphasized.

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Rebecca J. St George, Patricia Carlson-Kuhta, Kim J. Burchiel, Penelope Hogarth, Nicholas Frank and Fay B. Horak

Object

The effect of deep brain stimulation (DBS) for Parkinson disease (PD) on balance is unclear. The goal of this study was to investigate how automatic postural responses (APRs) were affected in patients randomized to either subthalamic nucleus (STN) or globus pallidus internus (GPi) surgery.

Methods

The authors tested 24 patients with PD who underwent bilateral DBS, 9 control patients with PD who did not undergo DBS, and 17 age-matched control volunteers. The electrode placement site was randomized and blinded to the patients and to the experimenters. Kinematic, kinetic, and electromyographic recordings of postural responses to backward disequilibrium via forward translations of the standing surface were recorded in the week prior to surgery while the patients were off (OFF) and on (ON) antiparkinsonian medication (levodopa), and then 6 months after surgery in 4 conditions: 1) off medication with DBS switched off (OFF/OFF); 2) off medication with DBS on (DBS); 3) on medication with DBS off (DOPA); and 4) with both medication and DBS on (DBS+DOPA). Stability of the automatic postural response (APR) was measured as the difference between the displacement of the center of pressure and the projected location of the center of body mass.

Results

Patients with PD had worse APR stability than controls. Turning the DBS on at either site improved APR stability compared with the postoperative OFF condition by lengthening the tibialis response, whereas medication did not show an appreciable effect. The STN group had worse APR stability in their best functional state (DBS+DOPA) 6 months after the DBS procedure compared with their best functional state (ON levodopa) before the DBS procedure. In contrast, the GPi group and the PD control group showed no change over 6 months. The APR stability impairment in the STN group was associated with smaller tibialis response amplitudes, but there was no change in response latency or coactivation with gastrocnemius.

Conclusions

Turning the DBS current on improved APR stability for both STN and GPi sites. However, there was a detrimental DBS procedural effect for the STN group, and this effect was greater than the benefit of the stimulating current, making overall APR stability functionally worse after surgery for the STN group.

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Lee T. Robertson, Rebecca J. St George, Patricia Carlson-Kuhta, Penelope Hogarth, Kim J. Burchiel and Fay B. Horak

Object

While deep brain stimulation (DBS) has proven to be an effective treatment for many symptoms of Parkinson disease (PD), a deterioration of axial symptoms frequently occurs, particularly for speech and swallowing. These unfavorable effects of DBS may depend on the site of stimulation. The authors made quantitative measures of jaw velocity to compare the relative effectiveness of DBS in the globus pallidus internus (GPi) or the subthalamic nucleus (STN). This was a randomized, double-blind, and longitudinal study, with matched healthy controls.

Methods

The peak velocities of self-scaled and externally scaled jaw movements were studied in 27 patients with PD before and after 6 months of bilateral DBS in the GPi or the STN. A mixed-effects model was used to identify differences in jaw velocity before DBS surgery (baseline) while off and on levodopa therapy, and after 6 months of DBS (postoperative) during 4 treatment conditions (off- and on-levodopa states with and without DBS).

Results

Self-scaled jaw velocity was impaired by the DBS procedure in the STN; velocity was significantly decreased across all postoperative conditions compared with either the off- or on-levodopa baseline conditions. In contrast, the postoperative velocity in the GPi group was generally faster than the baseline off-levodopa state. Turning the DBS off and on had no effect on jaw velocity in either group. Unlike baseline, levodopa therapy postoperatively no longer increased jaw velocity in either group, and this lack of effect was not related to postoperative changes in dose. The externally scaled jaw velocity was little affected by PD, but DBS still slightly affected performance, with the STN group significantly slower than the GPi group for most conditions.

Conclusions

The authors' results suggest that either the electrode implant in STN or the subsequent period of continuous STN stimulation negatively affected voluntary jaw velocity, including the loss of the preoperative levodopa-induced improvement. While the GPi group showed some improvement in voluntary jaw velocity postoperatively, their performance during the combination of DBS and levodopa was not different from their best medical management presurgery. The results have implications for DBS target selection, particularly for those patients with oromotor dysfunctions.