Spinal cord stimulation for intractable pain evaluated by a collision study using somatosensory evoked potentials: a preliminary report.

OBJECTIVE: Appropriate stimulation of the dorsal column is required in order to achieve optimal control over pain by way of spinal cord stimulation (SCS). In this study, we objectively evaluated changes in somatosensory evoked potentials (SEPs) during a collision test in order to investigate whether paresthetic sensation or amount of pain reduction was correlated with the degree of dorsal column stimulation. MATERIALS AND METHODS: We studied 12 patients with intractable pain who underwent permanent SCS implantation. SEP collision was examined while recording the cortical SEP components elicited by posterior tibial nerve stimulation. A positive collision effect was observed when the SEP amplitude was clearly reduced by the SCS. RESULTS: Based on the SEP collision findings, the effects of SCS were classified into four patterns: positive collision with pain reduction (Type 1), positive collision without pain reduction (Type 2), negative collision with pain reduction (Type 3), and negative collision without pain reduction (Type 4). Type 1 was observed for well-known diseases in which SCS was very effective, whereas Type 2 was seen in poor candidates for dorsal column stimulation. Patients with poststroke pain exhibited various patterns including types 1, 2, and 3. One patient showed Type 4 patterning, and we recommended further SCS trials before the abandonment of SCS therapy for this patient. CONCLUSIONS: We show that SEP collision is useful for evaluating the degree of dorsal column stimulation needed as well as in considering factors related to differences between responders and nonresponders to SCS therapy.

Late spinal cord metastasis of fourth ventricle ependymoma appeared nineteen years after the initial treatment.

Spinal cord dissemination (metastasis) of a fourth ventricle ependymoma more than ten years after surgical resection is extremely rare. In this report, we present an unusual case of a fourth ventricle ependymoma with metastasis to the thoracic spinal cord 19 years after the initial therapy, but without local recurrence. A 37 year-old patient underwent gross total resection of a fourth ventricle ependymoma and postoperative radiation therapy to the posterior fossa. Computed tomography (CT) scanning and/or magnetic resonance (MR) imaging performed during follow up examinations, conducted annually for ten years after the therapy, revealed no evidence of local tumor recurrence. However, 19 years after the initial treatment, the patient complained of back pain and gait disturbances. MR imaging revealed an intradural extramedullary tumor at the Th2-5 levels. MR imaging of the brain revealed no local tumor recurrence or intracranial tumor dissemination. Cerebrospinal fluid cytology revealed no presence of tumor cells. Total resection of the spinal cord tumor was performed, and the tumor was diagnosed as an ependymoma. We describe the clinical features of this rare lesion and particularly emphasize the need for long-term follow up, for more than ten years after the initial treatment, in patients with fourth ventricle ependymoma.

The Cross-Sectional Area of Paraspinal Muscles Predicts the Efficacy of Deep Drain Stimulation for Camptocormia.

BACKGROUND: Camptocormia, a disturbance of posture, is a well-described clinical feature of PD and other parkinsonian syndromes. Previous reports have shown that DBS of the subthalamic nucleus (STN) or globus pallidus internus is effective in treating camptocormia. However, the efficacy of DBS for camptocormia varies. OBJECTIVE: To determine a clinical marker for selecting an appropriate therapy for camptocormia, a disabling manifestation of Parkinson's disease (PD) that has a variable response to systemic and local therapies. METHODS: We obtained pre-operative lumbar magnetic resonance imaging of 14 consecutive PD patients with camptocormia who underwent subthalamic nucleus deep brain stimulation (STN-DBS) in this retrospective-designed study. Lumbar MRI was performed three to six months prior to the operation. We measured the cross-sectional area (CSA) and width of each participant's paraspinal muscles. RESULTS: Four (28.6%) patients were effective (EF), five (35.7%) were partially effective (PE), and five (35.7%) were non-effective (NE) to STN-DBS. The lumbar paraspinal CSA and width were significantly larger in the EF group than in the PE and NE groups. CONCLUSIONS: The CSA of paraspinal muscles and erector spinae width can be good predictive markers for improving camptocormia in patients with PD after deep brain stimulation.

The Effectiveness of the Stereotactic Burr Hole Technique for Deep Brain Stimulation.

Deep brain stimulation (DBS) is performed by burr hole surgery. In microelectrode recording by multi-channel parallel probe, because all microelectrodes do not always fit in the burr hole, additional drilling to enlarge the hole is occasionally required, which is time consuming and more invasive. We report a stereotactic burr hole technique to avoid additional drilling, and the efficacy of this novel technique compared with the conventional procedure. Ten patients (20 burr holes) that received DBS were retrospectively analyzed (5 in the conventional burr hole group and 5 in the stereotactic burr hole group). In the stereotactic burr hole technique, the combination of the instrument stop slide of a Leksell frame and the Midas Rex perforator with a 14-mm perforator bit was attached to the instrument carrier slide of the arc in order to trephine under stereoguidance. The efficacy of this technique was assessed by the number of additional drillings. Factors associated with additional drilling were investigated including the angle and skull thickness around the entry points. Four of the 10 burr holes required additional drilling in the conventional burr hole group, whereas no additional drilling was required in the stereotactic burr hole group (p = 0.043). The thicknesses in the additional drilling group were 10.9 ± 0.9 mm compared to 9.1 ± 1.2 mm (p = 0.029) in the non-additional drilling group. There were no differences in the angles between the two groups. The stereotactic burr hole technique contributes to safe and exact DBS, particularly in patients with thick skulls.

Clinical features of the localized girdle sensation of mid-trunk (false localizing sign) appeared in cervical compressive myelopathy patients.

Cervical compressive myelopathy patients sometimes show localized girdle sensation in the mid trunk (so-called false localizing sign). This symptom often confuses physicians, but the clinical features and mechanism of this symptom are still unclear. We investigated the clinical features and possible mechanism. In each of five cases of cervical compressive myelopathy disease with and without mid-truncal girdle sensation, the clinical features, degree and shape of cord compression were analysed. The girdle sensation was expressed as a vague or burning sensation, and was localized with a width of 3 or 4 dermatomes from the T3 to T11 level. There was no correlation between the appearance of the girdle sensation and etiology and level of cervical cord compression. Pyramidal tract signs and disturbance of superficial sensation were observed in all cases. Furthermore, on axial MRI, the midline ventral surface of the cervical cord was remarkably compressed in cases with girdle sensation, as if the compressive lesion entered the anterior medial fissure of the cervical cord. From these findings, this false localizing sign may be caused by severe compression of midline ventral structure of the cervical cord. Ischemia of the thoracic watershed zone of the anterior spinal artery from the compression of the anterior spinal artery at the cervical level might also be considered to be a possible cause.

Novel approach for the efficient use of a full-scale, 3-dimensional model for cervical posterior fixation: a technical case report.

STUDY DESIGN: Case report of a patient with atlantoaxial subluxation who underwent posterior cervical fixation. OBJECTIVE: To describe a novel approach for the efficient use of a full-scale, 3-dimensional model for preoperative planning and surgery. SUMMARY OF BACKGROUND DATA: Instrumented fusion of the cervical spine with screws and rods is indicated for atlantoaxial subluxation. Fatal complications, such as vertebral artery and spinal cord injuries, may occur during screw insertion. Making appropriate connecting rods, after screw insertion, is often time consuming. Therefore, precise preoperative planning and careful intraoperative procedures are required. METHODS: A 73-year-old male with atlantoaxial subluxation presented with progressive quadriplegia and gait disturbance. Surgery involving a C1 laminectomy and posterior cervical fixation was planned; and a 3D model, allowing visualization of the vertebral artery, was developed. Bilateral C1 and C4 lateral mass screws and C2 pars screws were experimentally inserted into the model. Rods with appropriate curvature were created to obtain rigid screw fixation, and were used during the surgery. Moreover, radiography and computed tomographic images of the instrumented model were analyzed to ensure the proper orientation of the screws. RESULTS: During surgery, screw insertion was performed, under fluoroscopic guidance, and compared with the 3D model and its preoperative radiographs. According to the preoperative analysis of the model-computed tomographic images, the direction of the C1 lateral mass screws was changed laterally, and the lengths of the C2 pars screws were shortened to avoid complications. The sterile, prebent rods could be elegantly adapted to the screws without additional bending. The postoperative course was uneventful, and postoperative computed tomographic images showed proper screw positioning. CONCLUSION: Three-dimensional models that allow (1) visualization of the vertebral artery, (2) evaluation of radiological images after screw insertion, and (3) the use of prebent rods during surgery contribute to the safety of the cervical posterior fixation. LEVEL OF EVIDENCE: N/A.

Neuroleptic malignant syndrome (parkinsonism-hyperpyrexia syndrome) after deep brain stimulation of the subthalamic nucleus.

Neuroleptic malignant syndrome (NMS), also called parkinsonism-hyperpyrexia syndrome (PHS), is a severe, general, sometimes fatal, physical reaction, induced by sudden and strong blockade of dopamine receptors. When subthalamic nucleus (STN)-deep brain stimulation (DBS) is used on patients with Parkinson disease (PD), dopaminergic medications are transiently stopped prior to the procedure, and a reduction in the use of drugs is routinely attempted after the procedure. Although a sudden stop or abrupt reduction of dopaminergic medications may set the stage for NMS/PHS, only three cases have been reported after STN-DBS surgery. Here, we describe a 75-year-old woman with PD who experienced delayed onset, yet fatal, PHS after STN-DBS. Although STN-DBS might prevent or suppress PHS, its protective effect is not always complete. We must be aware that fatal PHS can occur when the use of medication for PD is reduced or altered, even when patients are under continuous STN stimulation.

[Transient blindsight (type 2) after surgery for posterior cerebral artery aneurysm--case report].

In a 47-year-old woman experiencing pulsatile headache, radiological examination revealed a large right posterior cerebral artery (PCA) aneurysm. Preoperative neurological examination showed bilateral papilledema, but no visual disturbance. Cerebral angiography revealed that the aneurysm originated from the ambient segment of the PCA, and the posterior temporal, calcarine, and parieto-occipital arteries were all branched from the aneurysmal dome. Clipping of the feeding PCA trunk was performed via a left subtemporal approach. As a result of left occipital lobe infarction due to calcarine artery occlusion, right upper quadrant hemianopsia appeared after surgery, as confirmed by Goldman's perimetry. Other cerebral infarctions were identified in the junction between the left posterior internal capsule and thalamus, in the left posterior corpus callosum, and in the posterior base of the left temporal lobe due to the occlusion of the posterolateral thalamoperforating, posterior pericallosal, and posterior temporal arteries, respectively. The aneurysm was thrombosed and headache and papilledema subsided. The patient was able to detect the motion of a subject in a blind field, but consciousness of sight was absent. She was able to unconsciously move her finger toward a small penlight, and insert a paper into a slot with variable angles in the blind field. These phenomena disappeared within 4 months of the surgery. The results to forced choice tasks with figures (circle, cross, square, triangle, and star) and colors (red, blue, yellow, and green) were below chance levels. The present case was thus diagnosed as blindsight type 2 (gnosopsia) associated with awareness, probably due to transient activation of the dorsal "what" pathway among numerous visual processes.