Mayumi Kitagawa

Two-year follow-up of chronic stimulation of the posterior subthalamic white matter for tremor-dominant Parkinson's disease.

OBJECTIVE:To determine the efficacy and safety of unilateral deep brain stimulation on the posterior subthalamic white matter, including the zona incerta (ZI) and the prelemniscal radiation (PRL), for tremor-dominant parkinsonian patients and to determine the exact location of electrodes that were most effective. METHODS:Eight parkinsonian patients with severe resting tremor underwent unilateral stimulation of the ZI/PRL by use of stereotactic guidance. Electrophysiological targeting was obtained by macrostimulation and by somatosensory evoked potentials recorded directly through a quadripolar deep brain stimulation lead. Postoperative computed tomographic scans and magnetic resonance images were performed to confirm anatomic location of the electrode. Parkinsonian motor disabilities were evaluated by use of the Unified Parkinson’s Disease Rating Scale in the medication-off state before surgery and every 6 months after electrode implantations. RESULTS:The mean location of the clinically effective contacts was in the posterior subthalamic white matter, including the ZI and the PRL (mean, 5.6 ± 1.2 mm posterior to the midcommissural point, 3.2 ± 1.1 mm inferior to the anterior commissure-posterior commissure line, and 10.5 ± 1.2 mm lateral to the midline). At 24 months after operation, ZI/PRL stimulation resulted in significant improvement in mean Unified Parkinson’s Disease Rating Scale motor score by 44.3%, contralateral tremor by 78.3%, contralateral rigidity by 92.7%, and contralateral akinesia by 65.7% above the “off-stimulation” scores. Handwriting, posture, and gait were also improved. There were no or only mild adverse events. CONCLUSION:Unilateral ZI/PRL stimulation is a reliable and long-term therapeutic modality and can be considered another surgical target for the treatment of tremor-dominant Parkinson’s disease.

Deep brain stimulation of subthalamic area for severe proximal tremor

Article abstract Proximal tremors are often refractory to nucleus ventrointermedius thalami thalamotomy. Subthalamotomy has been suggested to be effective for treatment of tremor, although this procedure is associated with considerable adverse effects, and has rarely been considered a suitable treatment modality. The authors demonstrate the efficacy and safety of subthalamic deep brain stimulation in two patients, one with a severe, refractory proximal essential tremor and one with tremor with dystonia.

Relationship between antisaccades and the clinical symptoms in Parkinson's disease

We studied voluntary control of saccadic eye movement in 32 parkinsonian patients using the antisaccade task (the subjects were instructed not to look at the target but to look in the opposite direction). Mean latencies and error rates in the antisaccade task were significantly increased in advanced parkinsonian patients. The latencies of the antisaccades correlated with the severity of bradykinesia as well as the results of the Wisconsin Card Sorting Test. Patients taking anticholinergics showed significantly higher error rates. These results suggest that disturbance in the initiation of voluntary saccades in advanced patients may be associated with frontal lobe dysfunction, while anticholinergics may affect the inhibitory control of reflexive saccades.

Deficits of working memory during mental calculation in patients with Parkinson's disease.

Using the dual task paradigm, previous studies have suggested that working memory (WM) deficit is due to depleted attention resources in patients with Parkinsons disease (PD). The aim of this study is to establish whether the WM problems in PD are due to reduced attentional set-shifting resources rather than depletion of attention resources. The task design attempts to eliminate confounding of the deficits in dealing with novel material, a problem documented in PD, by concentrating on WM tasks of mental calculation that are familiar to subjects in daily living. We also administered attention tasks, the Trail Making Test (TMT) that relies primarily on attentional set-shifting and the Kana (Japanese syllabogram) Pick-out Test instead primarily depending on depleted attention resources for allocation. A total of 24 patients with PD and 24 normal controls participated in this study. The PD group showed deficits in mental calculation span and in attentional set-shifting in the TMT-b.Considering the common deficits in alternating processing of mental calculation and TMT-b in PD, the results suggested that the central executive dysfunction in PD during mental calculations was due to reduced attentional set-shifting resources for rapidly alternating operations, rather than the depletion of attentional resources.

Effects of caffeine on the freezing of gait in Parkinson's disease.

Caffeine is a nonselective competitive blockade of adenosine A1 and A2A receptors. In this report, we studied the efficacy of 100 mg of caffeine per day on the freezing of gait (FOG) for patients with Parkinsons disease. Different subtypes of FOG showed different therapeutic responses to caffeine. Caffeine improved “total akinesia” type of FOG, but had no effect on “trembling in place.” Tolerance developed to the beneficial effect of caffeine on FOG within a few months, but a 2‐week caffeine withdrawal period could restore the effect of caffeine.

Pure Topographical Disorientation Following a Right Forceps Major of the Splenium Lesion: A Case Study

A 72-year-old man with pure topographical disorientation following a focal hemorrhage in the right forceps major of splenium was assessed at 2 weeks and 3 months after the onset. Initially, he could identify familiar buildings and landmarks, but noted topographical disorientation, dysfunction in sense of quarters, and in visuo-spatial function. The improvement of topographical disorientation was attained in 3 months, while the inability of the sense of quarters and manipulating visuo-spatial information remained unchanged. These results suggested the heading disorientation was accompanied with impaired sense of quarters, although disabled sense of quarters continued beyond the recovery of heading disorientation.

Characteristics and distribution of somatosensory evoked potentials in the subthalamic region

OBJECT The aim of the present study is to evaluate the topographical distribution of somatosensory evoked potentials (SSEPs) in the subthalamic area, including the zona incerta (ZI). Determination of this distribution may help in the correct placement of deep brain stimulation (DBS) leads. METHODS Intraoperative SSEPs were recorded from contacts of DBS electrodes at 221 sites in 41 patients: three patients with essential tremor and 38 with Parkinson disease who underwent implantation of DBS electrodes for the relief of severe tremor or parkinsonism. RESULTS Two distinct SSEPs were recorded in the subthalamic area. One was a monophasic positive wave with a mean latency of 15.8 +/- 0.9 msec, which the authors designated subthalamic P16. Using both cephalic and noncephalic references, subthalamic P16 was only recorded in the ventral part of the ZI (mean 6.6 +/- 1.3 mm posterior to the midcommissure point, 4.8 +/- 1.2 mm inferior to the anterior commissure-posterior commissure line, and 9.7 +/- 0.6 mm lateral to the midline). When bipolar recordings were made, the traces showed a phase reversal at the caudal part of the ZI. The second potential is a positive-negative SSEP recorded throughout the entire subthalamic area. The mean latencies of the initial positive peak and the major negative peak were 13.6 +/- 1.1 msec and 16.4 +/- 1.1 msec, respectively. Several small notches were superimposed on the peaks, and their amplitudes were largest at the contact close to the medial lemniscus. CONCLUSIONS The results indicate that intraoperative SSEPs from DBS electrodes are helpful in refining stereotactic targets in the thalamus and subthalamic areas.