Masahiro Oinuma

Blood flow disturbance in perforating arteries attributable to aneurysm surgery

OBJECT The object of this study was to investigate patients with cerebral infarction in the area of the perforating arteries after aneurysm surgery. METHODS The authors studied the incidence of cerebral infarction in 1043 patients using computed tomography or magnetic resonance imaging and the affected perforating arteries, clinical symptoms, prognosis, and operative maneuvers resulting in blood flow disturbance. RESULTS Among 46 patients (4.4%) with infarction, the affected perforating arteries were the anterior choroidal artery (AChA) in nine patients, lenticulostriate artery (LSA) in nine patients, hypothalamic artery in two patients, posterior thalamoperforating artery in five patients, perforating artery of the vertebral artery (VA) in three patients, anterior thalamoperforating artery in nine patients, and recurrent artery of Heubner in nine patients. Sequelae persisted in 21 (45.7%) of the 46 patients; 13 (28.3%) had transient symptoms and 12 (26.1%) were asymptomatic. Sequelae developed in all patients with infarctions in perforating arteries in the area of the AChA, hypothalamic artery, or perforating artery of the VA; in four of five patients with posterior thalamoperforating artery involvement; and in two of nine with LSA involvement. The symptoms of anterior thalamoperforating artery infarction or recurrent artery of Heubner infarction were mild and/or transient. The operative maneuvers leading to blood flow disturbance in perforating arteries were aneurysmal neck clipping in 21 patients, temporary occlusion of the parent artery in nine patients, direct injury in seven patients, retraction in five patients, and trapping of the parent artery in four patients. CONCLUSIONS The patency of the perforating artery cannot be determined by intraoperative microscopic inspection. Intraoperative motor evoked potential monitoring contributed to the detection of blood flow disturbance in the territory of the AChA and LSA.

Rebleeding from ruptured intracranial aneurysms in North Eastern Province of Japan. A cooperative study

OBJECT Rebleeding from ruptured intracranial aneurysms is a major cause of death and disability. With regard to the factors that precipitate the rebleeding and influence the time course after initial bleeding, previous reports differ in their results, and the number of patients investigated was not sufficient for valid conclusions. This study was thus designed to clarify the factors related to rebleeding from ruptured intracranial aneurysms in a large group of patients of the North Eastern Province of Japan. METHODS We found 181 patients with rebleeding after hospitalization among 5612 cases of ruptured intracranial aneurysms from January 1997 to December 2001 in 33 major hospitals in the North Eastern Province of Japan. We analyzed the data with respect to the time course after bleeding and rebleeding, the arterial blood pressure, the situation when rebleeding occurred, the methods of neuroimaging, the level of consciousness, the treatment and the outcome. RESULTS Of 181 patients who were hospitalized, rebleeding occurred in 65 (35.9%) within 3 h and 88 (48.6%) within 6 h after the initial subarachnoid hemorrhage (SAH). The consciousness level before the rebleeding varied widely in distribution, but belonged to the drowsiness or less [Japan coma scale (JCS) single-digit] in 83 patients (45.8%), but after rebleeding, JCS triple-digits (semicoma to coma) included 152 patients (84.0%). Systolic arterial blood pressure prior to rebleeding was most commonly between 120 and 140 mmHg. Rebleeding did occur more frequently during angiography (totally 29 patients, 20%) and much less frequently during 3D-CTA and MRA procedures (a single case). Treatment consisted of aneurysm neck clipping in 72 patients (40.0%), endovascular therapy with coils in 4 patients (2.2%) and conservative ones in 103 patients (56.9%). As to outcome, 109 patients with rebleeding (60.2%) died in 3 months following initial SAH. CONCLUSION Rebleeding occurs more frequently in the earlier period after the initial SAH than previously believed. Thus, more aggressive pharmacologically induced systemic arterial hypotension appears to be important for preventing rebleeding but ultimate outcome of more aggressive hypotension is yet to be determined. If feasible, in order to avoid catheter-angiography related rebleeding, evaluations solely with 3D-CTA and MRA should be in consideration and earlier surgical intervention seems essential as rebleeding does occur often within the first 3 h of onset.

Utility and the limit of motor evoked potential monitoring for preventing complications in surgery for cerebral arteriovenous malformation.

OBJECTIVE To evaluate the usefulness of motor evoked potential (MEP) monitoring and mapping in arteriovenous malformation surgery. METHODS Intraoperative MEP monitoring was performed in 21 patients whose AVMs were located near the motor area or fed by arteries related to the corticospinal tract to detect blood flow insufficiency and/or direct injury to the corticospinal tract and/or to map the motor area. RESULTS In 4 of 16 patients monitored for blood flow insufficiency, the MEP changed intraoperatively. In 2 patients, the changes were attributable to temporary occlusion of the feeding artery (anterior choroidal or lenticulostriate artery): 1 patient had a venous infarction around the internal capsule caused by thrombosis of the draining vein and the other bled intraoperatively from the nidus. In 17 patients, the MEP was monitored to rule out direct injury. In 1 patient, the MEP changed on coagulation of fragile vessels around the nidus in the precentral gyrus; it recovered after coagulation was discontinued. In 1 of 5 patients with MEP changes, the MEP did not recover; permanent hemiparesis developed in this patient because of venous infarction. In 1 of 11 patients subjected to MEP mapping of the motor area, we found translocation to the postcentral sulcus. CONCLUSION In arteriovenous malformation surgery, MEP monitoring facilitates the detection of blood flow insufficiency and/or direct injury of the corticospinal tract and mapping of the motor area. It contributes to reducing the incidence of postoperative motor paresis.

HIGH-FREQUENCY MONOPOLAR ELECTRICAL STIMULATION OF THE RAT CEREBRAL CORTEX

OBJECTIVEIntraoperative monitoring of the motor-evoked potential has been widely used in patients undergoing neurosurgery. Direct stimulation of the brain with high-frequency monopolar stimulation (HFMS) is one of the most common methods to produce motor-evoked potential. We studied the influence of HFMS on the rat cerebral cortex. METHODSWe applied 1.5, 15, 30, 40, or 50 mA of HFMS to the rat sensorimotor cortex by a short sequence of five monopolar, monophasic, anodal rectangular 500-Hz pulses. We delivered one short five-pulse train 100 times every 5 seconds and examined pre- and post-stimulation electroencephalograms and histological changes at the stimulation site. RESULTSWe observed no spike waves after HFMS in any of the rats. There was no change in the power spectrum or frequency content in any of the rats exposed to HFMS. Histologically, there was significant swelling of the dendrites in rats sacrificed immediately after exposure to 40- and 50-mA stimulation; the 50-mA stimulation group also exhibited slight swelling of the mitochondria. These findings were not obtained in any of the rats sacrificed 30 days after stimulation. CONCLUSIONIn rats exposed to a stimulation intensity of 30-mA or less, no morphological or electrophysiological changes were observed. However, the possibility that HFMS may affect neural tissue cannot be ruled out.

Evoked potentials elicited on the cerebellar cortex by electrical stimulation of the rat spinocerebellar tract.

BACKGROUND In the current study, as a first step to develop a monitoring method of cerebellar functions, we tried to record evoked potentials on the cerebellar cortex by electrical stimulation of the rat SCT, which is located in the Inf-CPed. METHODS The experimental study was performed on rats. Unilateral muscular contractions of quadriceps femoris muscle were elicited by electrical stimulation. The evoked potentials were recorded from the surface of the ipsilateral cerebellum and the contralateral primary sensory cortex. RESULTS The highly reproducible potentials obtained from the ipsilateral cerebellar hemisphere were named SCEP. The SCEP exhibited one negative peak with a latency of 11.7 +/- 0.3 milliseconds (N(11)). Short-latency somatosensory evoked potential was recorded from the contralateral primary sensory cortex with a latency of 19.1 +/- 0.6 milliseconds. Coagulation of the ipsilateral Inf-CPed caused disappearance or marked reduction of the SCEP N(11), but it did not change the SSEP. On the other hand, sectioning of the ipsilateral dorsal column resulted in the disappearance of the SSEP, but it did not affect the SCEP N(11). CONCLUSIONS Reproducible SCEP was recorded from the rat cerebellar hemisphere by electrical stimulation of the quadriceps femoris muscle. We posit that the SCEP differs from the SSEP, which ascends via the dorsal column, and that it is conducted by the dorsal SCT located in the Inf-CPed. Our results suggest that it may be possible to detect the dysfunction of the Inf-CPed electrophysiologically by using SCEP.

Evaluation of cervical arteries with 3D-CTA using multi-detector row CT—one-session scanning of the head and neck using single or double injection of contrast medium

Abstract To detect cervical vascular lesions in 90 patients with intracranial cerebrovascular diseases, we performed three-dimensional CT angiography (3D-CTA) of the head and neck using multi-detector row CT (MD-CT) with a single- or double-bolus injection of contrast material. In the single-injection group (n=70), the head and neck were scanned in one session after continuous injection at a rate of 3 ml/s of contrast medium (total 100 ml). In the double-bolus injection group (n=20), the head was scanned first after the delivery of contrast material (3 ml/s, total 70 ml) and the neck was scanned after a boost injection (2 ml/s, total 30 ml). The single-bolus injection method was simple and suitable for screening for vascular lesions at the carotid bifurcations. The double bolus injection method yielded excellent 3D-CTA of the vertebral- and carotid arteries without interference by cervical veins and was suitable for screening the whole length of the carotid arteries, including the origin of the vertebral arteries. The head and neck 3D-CTA using MD-CT provides valuable diagnostic information regarding vascular lesions of the intracranial and cervical arteries.

Prevention of symptomatic vasospasm — effect of continuous cisternal irrigation with urokinase and ascorbic acid

Background Continuous cisternal irrigation (CCI) with urokinase (UK) and ascorbic acid (AsA) has been performed to prevent symptomatic vasospasm (SVS) after severe aneurysmal subarachnoid haemorrhage (SAH). To dissolve and wash out the SAH, CCI with urokinase is used. Ascorbic acid is added to degrade oxyhemoglobin, one of the strong spasmogenic substances. The efficacy and safety of this method were evaluated.

Dynamic MRI using a field echo for brain tumors

Abstract Thirty-seven patients with brain tumors were studied by dynamic magnetic resonance imaging (MRI) using a field echo method. The tumors included nine pituitary adenomas, nine schwannomas, eight meningiomas, three gangliogliomas, two metastatic brain tumors, two malignant lymphomas and four other brain tumors, which were histologically diagnosed. Sequential images were acquired every 15 s for 5 min after administration of Gd-DTPA. With setting of a region of interest (ROI) in the tumors, the signal intensity (S.I.) ratios were calculated. The time intensity curves of the S.I. ratios were investigated. The dynamic curves of the S.I. ratio could be classified into four patterns: (1) rapid increase followed by gradual decrease (pituitary adenoma, meningioma and germinoma); (2) gradual increase followed by plateau (schwannoma); (3) rapid increase followed by gradual increase (metastatic brain tumor, malignant lymphoma and ganglioglioma); (4) no or faint enhancement (craniopharyngioma, epidermoid and cavernous angioma). Our study indicated that the tumors had the characteristic patterns of the dynamic curve of S.I. ratios. Dynamic MRI using a field echo provides useful information for the differential diagnosis of brain tumors.

The surgery of ruptured and unruptured cerebral aneurysms using three-dimensional CT angiography without conventional catheter angiography

Abstract The object of this study is to assess whether aneurysm surgery can be performed in patients with ruptured and unruptured cerebral aneurysms by using three-dimensional computerized tomography angiography (3D-CTA) alone, without conventional catheter angiography (CCA). We have operated on 153 consecutive patients with ruptured aneurysms and 89 patients with unruptured aneurysms based on 3D-CTA findings since December 1996 and February 1997, respectively. In the cases of ruptured aneurysm, 153 ruptured aneurysms including 62 associated unruptured aneurysms were detected by 3D-CTA. CCA was performed in 7 of 153 patients after they underwent 3D-CTA, which included four dissecting vertebral artery (VA) aneurysms, two basilar artery (BA) tip aneurysms, and one BA–superior cerebellar artery (SCA) aneurysm. In 89 patients with unruptured aneurysms, 101 unruptured aneurysms were detected by 3D-CTA. In 5 of 101 unruptured aneurysms, which included giant or large aneurysms and a case of an aneurysm associated with infarction, CCA was needed. All of the ruptured and unruptured aneurysms were confirmed during surgery and treated successfully. The authors stress that 3D-CTA could replace CCA in the diagnosis of saccular aneurysms and that surgery could be performed in almost all ruptured and unruptured aneurysms by using only 3D-CTA without CCA.