Maaya Orii

Various patterns of the middle cerebral vein and preservation of venous drainage during the anterior transpetrosal approach

OBJECTIVE The drainage of the superficial middle cerebral vein (SMCV) has previously been classified into 4 subtypes. Extradural procedures and dural incisions during the anterior transpetrosal approach (ATPA) may interrupt the route of drainage from the SMCV. In this study, the authors examined the relationship between anatomical variations in the SMCV and the corresponding surgical modifications to the ATPA that are necessary for venous preservation. METHODS This study included 48 patients treated via the ATPA in whom the SMCV was examined using 3D CT venography. The drainage patterns of the SMCV were classified into 3 types: cavernous or absent (Type 1), sphenobasal (Type 2), and sphenopetrosal (Type 3). Type 2 was subdivided into medial (Type 2a) and lateral (Type 2b), and Type 3 was subdivided into vein (Type 3a), vein and sinus (Type 3b), and sinus (Type 3c). The authors performed 3 ATPA modifications to preserve the SMCV: epidural anterior petrosectomy with subdural visualization of the sphenobasal vein (SBV), modification of the dural incision, and subdural anterior petrosectomy. Standard ATPA can be performed with Type 1, Type 2a, and Type 3a drainage. With Type 2b drainage, an epidural anterior petrosectomy with subdural SBV visualization is appropriate. The dural incision should be modified in Type 3b. With Type 3c, a subdural anterior petrosectomy is required. RESULTS The frequency of each type was 68.7% (33/48) in Type 1, 8.3% (4/48) in Type 2a, 4.2% (2/48) in Type 2b, 14.6% (7/48) in Type 3a, 2.1% (1/48) in Type 3b, and 2.1% (1/48) in Type 3c. No venous complications were found. CONCLUSIONS The authors propose an SMCV modified classification based on ATPA modifications required for venous preservation.

Epidural anterior petrosectomy with subdural visualization of sphenobasal vein via the anterior transpetrosal approach—technical case report

The drainage of the superficial middle cerebral vein (SMCV) is classified into four subtypes. The sphenobasal vein (SBV) drains from the SMCV to the pterygoid venous plexus at the temporal skull base. Epidural procedures in the standard anterior transpetrosal approach (ATPA) may damage the route of the SBV. We report a case in which modified surgical procedures via the ATPA were used to preserve the SBV. A 45-year-old man complained of right facial pain. Magnetic resonance images revealed a right cerebellopontine tumor suggestive of an epidermoid cyst. Right carotid angiography revealed that the SMCV drained into the pterygoid venous plexus via the SBV. The convexity dura mater of the temporal lobe was cut and the anterior part of the temporal lobe was retracted subdurally. The SBV was visualized from the subdural side. The basal dura mater of the temporal lobe posterior to the SBV was cut and the posterior part of the temporal lobe was retracted epidurally. After dissecting the dura mater medial to the greater petrosal nerve and to the edge of the petrous apex, the petrous apex was exposed and drilled out without injuring the SBV. The superior petrous sinus and the tentorium were cut. The tumor compressed the root exit zone of the trigeminal nerve. The tumor was grossly totally removed. The modified ATPA (epidural anterior petrosectomy with subdural visualization of the SBV) is effective in preserving the SBV.

Anterior Transpetrosal Approach Combined with Partial Posterior Petrosectomy for Petroclival Meningiomas with Posterior Extension

BACKGROUND An anterior transpetrosal approach (ATPA) is suitable for treating upper petroclival lesions. However, the limit of the ATPA is reached when the tumor extends posterolaterally over the internal auditory canal (IAC) along the petrous edge. In such cases, ligation of the posterior part of the superior petrosal sinus (SPS) is necessary. To overcome this limitation, we combined the ATPA with a partial posterior petrosectomy in 8 patients who had petroclival meningiomas extending posterolaterally over the IAC. METHODS We resected only the Trautmann triangle in addition to the Kawase triangle to secure the space to ligate the posterior portion of the SPS. Because the tympanic cavity and bony labyrinth of the ear were not exposed, we were able to preserve hearing function and lower the risk of cerebrospinal fluid leakage. Furthermore, this approach enables easy ligation of the SPS and the tentorium posterior to the tumor attachment. This combined technique also allows visualization of the petrosal vein, which is important for surgery of the posterior fossa. RESULTS Total and near-total tumor removal was achieved in 6 patients (75%) with no permanent complications and no cerebrospinal fluid leakage. Postoperative hearing impairment was not found in any of the patients who underwent this surgery. CONCLUSIONS The ATPA combined with partial posterior petrosectomy is an effective method for removal of complicated petroclival meningiomas that extend posterolaterally over the IAC along the petrous edge.

Motor-related intracortical steal phenomenon detected by multichannel functional near-infrared spectroscopy imaging.

Background: Patients with severe cerebral ischemia may lose autoregulation to increase cerebral blood flow following neural activity. Although the steal phenomenon under conventional cerebral blood flow study has been known as a high-risk factor for stroke, the cerebral oxygen hemodynamics in ischemic patients during functional activation has not been thoroughly investigated. In this study, we present rare cases with intracortical steal phenomenon during motor tasks detected by multichannel functional near-infrared spectroscopy before and after surgery. Methods: The relative concentration change of oxygenated, deoxygenated and total hemoglobin in and around the primary sensorimotor cortex during contralateral hand grasping was investigated in 11 patients with severe internal carotid artery stenosis. Results: In 3 patients, the concentration of total hemoglobin around the primary sensorimotor cortex significantly decreased in response to motor stimulation and returned to baseline soon after termination of the motor task. This phenomenon partially disappeared postoperatively in all patients who underwent surgery. The remaining 8 patients showed no signs of total hemoglobin decrease in and around the sensorimotor cortex. In 9 patients, lack of decrease in deoxygenated hemoglobin in the center of the primary motor cortex during the motor task was observed and 3 of them showed significant increase in deoxygenated hemoglobin. Conclusions: We have demonstrated that in some patients with severe ischemia, an abnormal motor-related steal phenomenon can be observed. This phenomenon can be modulated by surgical intervention and might imply the severity of ischemia.

TP1.1 Correlation between intracortical inhibition and clinical symptoms in Parkinson’s disease: TMS study of patients with deep brain stimulation

Background: Impaired intracortical inhibition (ICI) in the motor cortex has been observed in Parkinson’s disease (PD) patients. The relationship between the ICI and clinical features in PD is, however, not well understood. Objectives: In order to examine effects of deep brain stimulation of the subthalamic nucleus (STN-DBS) on the ICI and investigate a correlation between the ICI and clinical symptoms in PD, changes of ICI and clinical symptoms in PD were measured after STN-DBS was turned off. Subjects and methods: Seven PD patients (50–72 years old) with STN-DBS were studied. The medication had been stopped more than 12 h before the study. ICI and clinical symptoms (rigidity and tremor) were measured before and 0, 10, 20, 30, 60 and 120 min after STN-DBS was turned off. ICI of the left motor cortex was examined using transcranial magnetic stimulation (TMS); silent period (SP) and motor evoked potentials evoked by paired pulse TMS with inter-stimulus interval of 2 ms (SICI) were measured. One of our staff, who was blind to the status of STN-DBS, recorded the degrees of rigidity and tremor in the right hand. TMS study was also performed on seven age-matched normal volunteers. Results: Even with STN-DBS on, PD patients showed shortened SP and decreased SICI, compared with normal controls. The SICI decreased significantly 10 min after DBS was turned off, while SP was shortened significantly 120 min later. Both of the symptoms, rigidity and tremor, worsened significantly 10 min after STN-DBS was turned off. Discussion: The decrease of SICI seemed to be correlated with deterioration of rigidity and tremor in PD. SP also reflected abnormal ICI but did not show the similar time course pattern with those of clinical features and SICI. Our results suggest that SP and SISI may not reflect an identical inhibitory system and that more than one ICI system may be impaired in PD, which can be effectively improved by STN-DBS.