In the surgical strategies for tremor control, there are distinct differences between thalamotomy and thalamic deep brain stimulation (DBS). In thalamotomy, the best therapeutic effect can be achieved by minimal coagulation placed precisely at the most appropriate target area. This strategy for thalamotomy may require the supposition that the most appropriate target area is located within a small restricted region. In DBS, the best therapeutic effect can be achieved by placing electrodes covering areas that should be stimulated to control tremor. This strategy for DBS does not always require the supposition that such areas are located within a small restricted region. According to some reports, when coagulation is localized in the nucleus ventralis intermedius, thalamotomy produces the most appropriate therapeutic effect on tremor. In contrast, the most appropriate therapeutic effect of DBS on tremor was obtained when the electrodes covered wide areas extending from the nucleus ventralis oralis anterior and posterior to the nucleus ventralis intermedius. In the case of DBS surgery, therefore, the orientation of the DBS lead is critically important in covering these nuclei. In addition, dual-lead DBS is useful for covering wide areas that require stimulation to control tremor.

View full abstract

Neurosurgeons are generally not familiar with dystonias. It is not, however, a rare condition and there are more than 10 patients per 100,000 general population. In recent years various neurosurgical interventions have been proven to be effective for various types of dystonias. For example, generalized dystonia involving whole the body and resulting in bed-ridden state can be dramatically improved with stereotactic chronic deep brain stimulation of the globus pallidum interna. Cervical dystonia is the most common among dystonias and exhibits symptoms of spasmodic torticollis. The first treatment of choice is local injection of botulinum toxin. But if the symptoms are refractory to the conservative treatment, selective peripheral denervation of the involved muscles is a well-established safe and effective surgical method. Task-specific focal hand dystonia, often called as writer's cramp, is no longer a psychogenic condition. Ventrooralis thalamotomy interrupting the oscillatory hyperactive cortico-pallidothalamic circuit results in excellent relief of the symptom of writer's cramp. Thus, in the modern era of functional neurosurgery, we neurosurgeons should regard most dystonias as a definite neurosurgical condition. In this review, we describe the current state of neurosurgical treatment for dystonias.

View full abstract

Deafferentation pains are very difficult to treat by medication and surgical techniques, and there is no established strategy. Until today, many kinds of ablation surgeries were tried for deafferentation pains. Now electrical stimulation therapies (spinal cord stimulation, deep brain stimulation and motor cortex stimulation) are currently used, because these techniques are less invasive and more effective. At this time, I would like to summarize the current treatments and discuss cortical (motor cortex) stimulation therapy (MCS). MCS has been reported to be effective on thalamic pain, phantom limb pain and CRPS. As a standard MCS technique, a resume was placed in the epidural space with SEP measuring to determine the central sulcus. We placed a grid electrode in the subdural space to decide upon the best stimulation point for pain relief over a few weeks with the purpose of determining the placement of a resume. In several patients, resumes were implanted in the interhemispheric fissure to reduce lower extremity pain. In seven patients, resumes were placed within the central sulcus to stimulate area 4 and area 3b directly. In addition, electrodes were also placed on the surface of the precentral gyrus. To date, 75% of the patients in our institute showed pain reduction. Our results indicated that area 4 within the central sulcus may be the optimal stimulation point for pain relief. We speculate that conventional method may sometimes fail to stimulate area 4 and that focal stimulation of area 4 within the central sulcus may improve the efficacy of this treatment. Our pharmacological tests show that the mechanism of deafferentation pain seems to be complicated, but patients with ketamine sensitivity seem to be good candidates for MCS. The MCS mechanism is unknown. A study with positron emission tomography showed that CBF increases in the thalamus, anterior cingulate, rectal gyrus and brainstem after MCS, but rarely in the sensory cortex. The efficacy of MCS is mainly related to increased synaptic activity in the thalamus, while activations in the rectal gyrus, anterior cingulate and frontal cortex may be rather related to emotional processes. MCS is a good and less invasive treatment for deafferentation pain, especially for thalamic pain, but the success rate is not 100%. In the case of MCS failure, we should choose spinal cord stimulation and deep brain stimulation especially for peripheral deafferentation pain.

View full abstract

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a good treatment of choice for patients with advanced Parkinson's disease, where motor fluctuations affects their daily activities. STN-DBS improves their off-stage motor symptoms, and also achieves their equivalent on〜stage with a lower L-DOPA dosage. The STN-DBS improves almost all cardinal symptoms of Parkinson's disease, and its spectrum of clinical effect resembles to that of L-DOPA. Axial symptoms and freezing improve less with STN-DBS than other motor symptoms. And no improvement is expected with STN-DBS in end-stage patients, where the administration of L-DOPA does not improve their symptoms. Though GPi-DBS also provides improvement of off-stage symptoms, their degree of improvement does not exceed those of STN-DBS. Several authors report postoperative confusion, depression, and impairment of higher cortical function as complications of STN-DBS, which was little reported with GPi-DBS.

View full abstract

Middle cerebral artery aneurysms arise mostly at the bifurcation of the horizontal part (Ml) of the middle cerebral artery. In many cases, proper dissection of the sylvian fissure allows observation of the whole aneurismal structure, so that neck clipping is not so difficult. However, care should be taken to avoid postoperative morbidity in particular cases including a short Ml, broad neck, and atherosclerosis of the neck/body. Surgical techniques for those cases are described in detail.

View full abstract

Internal carotid aneurysms at the bifurcation of the posterior communicating artery are common, but require some surgical techniques to be clipped in a safe manner. We must carefully observe the location of the posterior communicating artery as well as the perforating arteries, which should always be preserved. The dome of the aneurysm sometimes adheres to the tissues of the skull base and the pressure of the aneurysm is high. Therefore, proximal flow control is sometimes necessary when clipping aneurysms to prevent the aneurysm from rupturing. Because there was arteriosclerosis of the ophthalmic segment of the internal carotid artery, proximal flow control was undertaken at the cervical portion. Knowledge of the anatomy and variations of aneurysms at this portion and basic surgical techniques were necessary to finish the surgery without causing a catastrophic sequel.

View full abstract

The surgical strategies for anterior communicating aneurysms (Acorn) are discussed based on their topographical anatomy. Since this type of aneurysm locates at the lamina terminalis cistern, the dissection of the interhemispheric fissure is essential for its exposure. The pterional approach, which is most commonly used for this aneurysm, can be divided into two different approaches. The subfrontal approach consists of a subfrontal route followed by an interhemispheric route, which requires the further retraction or even evacuation of rectal gyrus. On the other hand, the transsylvian approach with sufficient dissection of the Sylvian fissure can theoretically present a straight route directly to the Acorn complex, and it also presents a wider operative field. The preservation of the Acorn perforators, which affects postoperative memory disturbance, can also be achieved by meticulous observation through the wide operative field. Thus, sufficient dissection of the Sylvian fissure and interhemispheric fissure followed by the transsylvian approach is important for the less-invasive surgery of anterior communicating aneurysms based on the anatomical point-of-view.

View full abstract

We reported a rare case of cerebellar malignant glioma fed by meningeal branches of the external carotid artery. A 77-year-old female was admitted to our hospital because of headache, nausea, and dizziness. Magnetic resonance imaging (MRI) showed a poorly circumscribed, heterogeneously enhanced lesion along the tentorium in the left cerebellar hemisphere. Left external carotid arteriography demonstrated a marked tumor stain fed by the left accessory meningeal artery. Subtotal removal of the tumor was carried out by left suboccipital craniectomy. The tumor arose from the left cerebellar hemisphere, extending along the tentorium, and was fed by many fine arteries from the dura mater which attached to the tumor. The histological diagnosis was malignant diffuse astrocytoma. A cerebellar malignant glioma fed by meningeal branches of the external carotid artery is extremely rare. It was very difficult to differentiate this type of tumor from meningioma and metastatic brain tumor before the operation.

View full abstract

We present a case of recurrent subarachnoid hemorrhage (SAH) attributed to rupture of an aneurysm which was not treated because it was not clearly seen on angiography at the first SAH. A 67-year-old woman presented with consciousness disturbance (Hunt & Kosnik grade IV) and left hemiparesis. A CT scan revealed massive SAH (Fisher group 3). Angiography showed a 5mm right carotid cave aneurysm and a bulging at the posterior communicating artery origin which was thought to be an infundibular dilatation. Emblization for the carotid cave aneurysm was successfully performed. Sudden consciousness disturbance occurred 7 days after embolization, and CT scan revealed recurrent SAH. Because of severe brain swelling due to vasospasm, the patient was treated conservatively. After a ventricle-peritoneal shunt was performed for normal pressure hydrocephalus, the patient recovered but had a left hemiparesis. Angiography obtained two months after embolozation showed complete occlusion of the previously embolized aneurysm, and the enlarged aneurysm thought to be an infundibular dilatation, previously. Both episodes of SAH were considered to be attributed to this aneurysm. Because it was a very small aneurysm, endovascular treatment was considered extremely difficult and dangerous. But at the request of her family, we performed endovascular embolization of aneurysm successfully. Postoperative course of the patient was uneventful. We stressed that early follow-up angiography is very important even after successeful occlusion of small carotid cave aneurysms because small carotid cave aneurysms tend not to rupture and another aneurysm which was unclear at the first angiography may appear clearly, after a while as in to our case.

View full abstract