Anterior interhemispheric approach for clipping of subcallosal distal anterior cerebral artery aneurysms: case series and technical notes.

Distal anterior cerebral artery (DACA) aneurysms are rare, accounting for 1-9% of all intracranial aneurysms. Previous systematic reviews have highlighted that given the markedly increased incidence of major complications after endovascular treatment, microsurgical clipping is the more attractive treatment option with generally excellent clinical outcomes. Subcallosal DACA aneurysms constitute a rare subset of these aneurysms, requiring special anatomic considerations-particularly with regard to the approach. The aim of this study is to review the technical nuances of microsurgical treatment of subcallosal DACA aneurysms, including review of contemporary techniques through presentation of a microneurosurgical operative video. This is a retrospective case series and intraoperative microsurgical videos review. Three subcallosal DACA aneurysms were identified via retrospective query of our institutional neurosurgical database from December 2017 to May 2018. Two were female; median age was 74 years (range 70-83); all 3 underwent bifrontal craniotomy via bicoronal skin incision for aneurysm clipping. Aneurysms were located in left pericallosal-callosomarginal artery junction, bifurcation of azygos A2, and pericallosal artery related with azygos A2, and the anterior interhemispheric approach was used in all 3 operations. No acute stroke, hemorrhage, or major complications occurred, and all patients remained neurologically intact at the time of last follow-up (median 3 months, range 1-6). Although DACA aneurysms are rare, they represent an important variant for cerebrovascular neurosurgeons where microsurgical clipping can have better angiographic outcomes than endovascular treatment. Detail-oriented anterior interhemispheric arachnoid dissection through bifrontal craniotomy with its lower margin sitting at the superior orbital rim maximizes safe and effective clipping of subcallosal DACA aneurysms.

[Malignant Transformation of Cerebellopontine Angle Epidermoid Cyst:A Case Report].

Intracranial epidermoid cysts are benign cystic lesions that typically exhibit slow growth. Their malignant transformation into squamous cell carcinoma is rare. We report a 77-year-old woman who was admitted to our hospital because of a near-drowning incident due to a seizure sustained in her bathtub. Magnetic resonance imaging(MRI)revealed an extra-axial tumor occupying the right cerebellopontine angle. The lesion appeared hyperintense in diffusion-weighted images and exhibited contrast enhancement after gadolinium injection. Cerebrospinal fluid examination revealed noninfectious meningitis, presumably due to the ruptured epidermoid cyst. Tumor resection was performed and histopathological examination revealed squamous cell carcinoma, which was indicative of malignant transformation of the cyst. The patient underwent adjuvant radiotherapy and has no signs of recurrence 9 months postsurgery. Rapid neurological deterioration and contrast enhancement on MRI are key signs of malignant transformation of epidermoid cysts.

Intelligent control of neurosurgical robot MM-3 using dynamic motion scaling.

OBJECTIVE Advanced and intelligent robotic control is necessary for neurosurgical robots, which require great accuracy and precision. In this article, the authors propose methods for dynamically and automatically controlling the motion-scaling ratio of a master-slave neurosurgical robotic system to reduce the task completion time. METHODS Three dynamic motion-scaling modes were proposed and compared with the conventional fixed motion-scaling mode. These 3 modes were defined as follows: 1) the distance between a target point and the tip of the slave manipulator, 2) the distance between the tips of the slave manipulators, and 3) the velocity of the master manipulator. Five test subjects, 2 of whom were neurosurgeons, sutured 0.3-mm artificial blood vessels using the MM-3 neurosurgical robot in each mode. RESULTS The task time, total path length, and helpfulness score were evaluated. Although no statistically significant differences were observed, the mode using the distance between the tips of the slave manipulators improves the suturing performance. CONCLUSIONS Dynamic motion scaling has great potential for the intelligent and accurate control of neurosurgical robots.

Dorsal displacement of the facial nerve in acoustic neuroma surgery: clinical features and surgical outcomes of 21 consecutive dorsal pattern cases.

In acoustic neuroma surgery, the facial nerve (FN) course varies among patients, but a dorsal pattern is rarely observed. We retrospectively reviewed and classified 556 acoustic neuromas operated on via a lateral suboccipital retrosigmoid (LSO) approach into two groups: dorsal (group D) and non-dorsal (group ND). The clinical features and outcomes including functional preservation of the FN, the extent of tumor resection, and the retreatment rate were compared. Among 556 cases, 21 (3.8%) patients with dorsal patterns were identified. No significant differences in clinical features or preoperative status were noted between groups D and ND. No significant differences in functional FN preservation were found between groups D and ND in the immediate postoperative period (90.5 and 83.0%, respectively) or 1-year postoperatively (95.2 and 97.0%, respectively). Compared with group ND, the extent of tumor resection was significantly less (p < 0.0001) and the retreatment rate was significantly higher in group D (hazard ratio, 33.6; 95% confidence interval [CI], 11.7-96.1; p < 0.0001). In one dorsal pattern case, surgical resection was abandoned based on the intraoperative findings. Dorsal displacement of the FN was accurately predicted with preoperative imaging evaluations in just two cases. Functional preservation of the FN during acoustic neuroma surgery is achievable if the FN runs along the dorsal side of the tumor. However, a dorsal pattern, especially when the FN is broadened, is clearly associated with less complete tumor removal and a higher rate of retreatment than typical pattern cases.

Clinical features of vestibular schwannomas in patients who experience hearing improvement after surgery.

Postoperative improvements in hearing in patients with vestibular schwannoma are extremely rare. We reviewed nine cases retrospectively to investigate the clinical features of these cases. Hearing improvement was defined as an improvement in hearing class according to American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) criteria. The nine patients comprised five men and four women with a mean age of 40.4 years. Of the nine tumors, three were solid and six cystic; mean tumor size was 29.7 mm. Mean pure tone average (PTA) and mean speech discrimination scores (SDS) were 47.5 dB and 22.8%, respectively, preoperatively and 29.6 dB and 83.9%, respectively, postoperatively. AAO-HNS class distribution was class B:1 and D:8, preoperatively, and class A: 5 and B:4, postoperatively. A lateral suboccipital retrosigmoid approach with a lateral (park bench) position was used in all nine patients. Clinical features of these vestibular schwannomas included (1) large cystic tumors, (2) sudden onset hearing loss, (3) the presence of a valley shape in the middle-pitch area on preoperative audiograms, (4) almost intact preoperative inner ear function, (5) a low SDS relative to PTA preoperatively, (6) surgical treatment via a lateral suboccipital approach within 6 months of the most recent exacerbation of hearing loss, (7) observation of I waves in preoperative, intraoperative, and postoperative auditory brainstem response (ABR) recordings, and (8) postoperative improvement in mainly the middle-pitch range and SDS. For surgical treatment of vestibular schwannomas with the above clinical features, a translabyrinthine approach and cochlear nerve section (unless the I wave on the intraoperative ABR trace disappears) should be avoided, regardless of the patient's preoperative hearing level, if a surgeon hopes to maximize the chances of preserving or improving hearing.

[An Endovascular Approach for Ruptured Aneurysms of the Basilar Trunk Perforating Artery].

Aneurysms of the basilar trunk perforating artery are rarely described in the literature. Only 13 cases have been reported previously. The recommended treatment for these aneurysms is usually direct surgery such as microsurgical clipping or proximal trapping;endovascular therapy is not preferred because of difficulty to access the aneurysm. Recently however, a case report of treatment of basilar trunk perforating aneurysm with a Pipeline Embolization Device was published. Microsurgical clipping or wrapping has the disadvantage of the deep and narrow operative area and the difficult skull-base technique. Here, we report a case of basilar trunk perforating rupture aneurysm and its treatment with endovascular coil embolization.

Hydrocephalus associated with vestibular schwannomas: perioperative changes in cerebrospinal fluid.

BACKGROUND: Cerebrospinal fluid (CSF) protein levels are known to increase in patients with vestibular schwannomas (VS) with concomitant hydrocephalus, however the only information available on perioperative changes in CSF in these patients comes from case reports. Here, we investigated the relation between CSF protein and hydrocephalus in a large series of patients undergoing resection of VS. METHOD: We classified 376 patients undergoing resection for VS at our institute into two groups, namely VS and no hydrocephalus (control, n = 319) and VS with concomitant hydrocephalus (n = 57), and compared clinical parameters. Among the 57 patients diagnosed with hydrocephalus, hydrocephalus status was examined by lumbar puncture in 20 patients with communicative hydrocephalus, and pre- and postoperative scores in CSF properties were compared. RESULTS: Patients in the hydrocephalus group were significantly older than those in the control group (mean, 55.8 vs. 43.8 years), and had a longer disease duration (median, 76 vs. 12 months), larger tumors (median, 15.6 vs. 5.5 ml), and a higher protein concentration in CSF (median, 147.3 vs. 65.1 mg/dl). Perioperative CSF samples of hydrocephalus patients showed a significantly decrease in cerebrospinal pressure after tumor removal (median, -75mmH2O), followed by a decrease in CSF protein (median, -74.5 mg/dl). No patients required the placement of a shunt. CONCLUSIONS: Extended disease duration and elevated CSF protein secondary to the presence of a tumor contribute to the occurrence of hydrocephalus. Primary maximal tumor removal for VS with coexisting hydrocephalus avoids an unnecessary shunt.

Primary Intracranial Spindle Cell Sarcoma, DICER1-Mutant, with MDM2 Amplification Diagnosed on the Basis of Extensive Molecular Profiling.

Primary intracranial spindle cell sarcoma is an extremely rare mesenchymal tumor, the molecular pathogenesis of which is poorly understood. Because of the lack of specific markers, diagnosis sometimes relies on ruling out all possible differential diagnoses, often making it difficult to reach a definitive diagnosis. In this case study, we report a 69 year-old female patient for whom the integration of multi-layered molecular analyses contributed to making the diagnosis. The disease exhibited aggressive clinical behavior, requiring two sequential surgeries because of rapid regrowth within a short period. Primary and recurrent tumors exhibited similar histological features, in which spindle-shaped cells arranged in interlacing fascicles without any specific architectures, implicating sarcomatous tumors. In immunohistochemistry testing, tumor cells were immunopositive for vimentin but lacked any specific findings that contribute to narrowing down the differential diagnoses. Seeking further diagnostic clues, we performed DNA methylation-based analysis. The copy number analysis revealed MDM2 gene amplification and loss of heterozygosity of 22q. Moreover, dimension reduction clustering analysis implicated a methylation pattern comparable to aggressive types of sarcomas. In addition, an in-house next-generation sequencing panel ("Todai-OncoPanel") analysis identified somatic mutations in DICER1, NF2, and ATRX genes. Taken all together, we finally made the diagnosis of primary intracranial spindle cell sarcoma, DICER1-mutant, with MDM2 gene amplification. This case report suggests that even for the tumors with insufficient morphological and immuno-histological diagnostic clues, integration of multi-layered molecular analyses can contribute to making the diagnoses as well as to understanding the rare tumors by elucidating unexpected genetic and epigenetic features.

Intraoperative continuous monitoring of evoked facial nerve electromyograms in acoustic neuroma surgery.

BACKGROUND: Preservation of facial nerve function is one of the most important goals in acoustic neuroma surgery. We have been using intraoperative continuous monitoring of evoked facial nerve electromyograms (EMGs) since 1997 in acoustic neuroma surgery. We therefore investigated surgically treated patients to clarify the usefulness of this monitoring, and to determine safety criteria for preserving facial nerve function. METHODS: This intraoperative continuous monitoring of evoked facial nerve EMG is a method for checking the EMG evoked by continuous direct electrical stimulation of the facial nerve during tumor excision. The greatest advantage of this method is the ability to identify changes in EMG in real time. We retrospectively investigated 216 patients with surgically treated acoustic neuroma to identify correlations between parameters in this monitoring and postoperative facial nerve function immediately and 1 year after surgery. RESULTS: In these patients, the functional preservation rate of the facial nerve (House and Brackmann grade 1 or 2 at 1 year after surgery) was 98.6% with a 98.2% mean tumor resection rate. Amplitude preservation ratio correlated significantly with facial nerve function both immediately and 1 year after surgery. To avoid severe facial nerve palsy, a warning criterion of amplitude preservation ratio >50% appears useful. CONCLUSIONS: Postoperative course of facial nerve function appears predictable using intraoperative continuous monitoring of evoked facial nerve EMGs. This monitoring is useful to increase the tumor excision rate while avoiding severe postoperative facial nerve palsy in acoustic neuroma surgery.

Resection of a lateral supratentorial endodermal cyst complicated by postoperative seizures: A case report.

BACKGROUND: Endodermal cysts are uncommon cystic lesions usually located at the ventral aspects of the spine. A lateral supratentorial location of such cysts is extremely rare. A unique case of a lateral supratentorial endodermal cyst that required surgical intervention due to uncal herniation, complicated with postoperative seizures, is presented. CASE DESCRIPTION: A 48-year-old man presented with transient motor aphasia and diplopia. Magnetic resonance imaging showed a cystic lesion occupying the left frontal and temporal convexity with midline shift and uncal herniation. Cyst resection was performed, and cyst contents with mucous-like components were aspirated. Histopathological examination showed an endodermal cyst. The patient showed no neurological deficits immediately after surgery but developed tonic-clonic seizures 9 h after surgery. Sedation and intubation were required to control the seizures. After administering multiple antiepileptic drugs, he was extubated on the 5th day after surgery. He was discharged home in a month with mild impairment in dexterity of his right hand. CONCLUSIONS: Surgical intervention for endodermal cysts can be complicated by postoperative seizures caused by chemical irritation of brain cortex due to spillage of cyst contents. It is important to irrigate the cyst wall very well intraoperatively and pay attention not to spill the cyst fluid to unaffected locations. Preoperative administration of antiepileptic drugs should also be considered if endodermal cysts, not simple arachnoid cysts, are suspected preoperatively.

Retrosigmoid Intradural Suprajugular Approach to Jugular Foramen Tumors with Intraforaminal Extension: Surgical Series of 19 Cases.

OBJECTIVE: The intraforaminal component of jugular foramen tumors is difficult to access surgically, as it requires complex approaches for radical removal and leads to a high recurrence due to residual tumor. The retrosigmoid suprajugular approach, intradural drilling of the roof of the jugular foramen, has been recently proposed for removal of such intraforaminal component without sacrificing the sigmoid-jugular venous system or requiring additional approaches. This study presents our experience with this approach and introduces the use of intraoperative continuous vagus nerve monitoring. METHODS: Nineteen patients (14 with neuromas and 5 with meningiomas) were operated using this approach over a 12.5-year period. In the more recent 14 cases, continuous vagus nerve monitoring was performed with a ball-type electrode placed on the proximal vagus nerve. RESULTS: More than 95% of the tumor removal was achieved in all but the first neuroma case. Extubation immediately after surgery and oral feeding within a week postoperatively was achieved in all patients. Seven of 9 patients with preoperative hearing disturbance symptomatically improved after surgery. All but the first case had no signs of recurrence during the follow-up period (average of 58 months). CONCLUSIONS: The retrosigmoid suprajugular approach is safe and effective for removal of tumors extending into the jugular foramen, maintaining a chance of hearing improvement. Intraoperative continuous vagus nerve monitoring is useful to avoid postoperative complications in such surgeries.

The Method for Placement of an Intraoperative Continuous Facial Nerve Stimulating Electrode in Acoustic Neuroma Surgery: Technical Note.

Preservation of facial nerve (FN) function is the most important goal in acoustic neuroma (AN) surgery. We have been using intraoperative continuous facial nerve monitoring (ICFNm) of evoked electromyography during AN surgery. ICFNm is very useful, and we can identify the real-time functions of the FN. Some surgeons have experienced difficulty with placing the ICFN stimulating electrode (SE). We therefore show how to place the ICFN SE. We mostly perform AN surgery with a retrosigmoid approach (RSA). A craniotomy with four burr holes is performed. We dissect the arachnoid membrane along the accessory nerve from the cisterna magna to the glossopharyngeal nerve. When we are able to identify the root exit zone (REZ) of the FN near the brainstem, we place the ICFN SE on it. However, when a large tumor covers the REZ, we have to debulk the tumor to create a space between the tumor and the glossopharyngeal nerve. After that, we can place the SE on the REZ. A method for placement of the ICFN SE is needed for some techniques of AN surgery. Once we learn how to place the SE, we can identify continuous FN function during AN surgery. This method is useful for the preservation of postoperative FN function in AN surgery.

Intramedullary and intratumoral hemorrhage in spinal hemangioblastoma: Case report and review of literature.

BACKGROUND: Intramedullary hemorrhages involving spinal hemangioblastomas are rare. They are frequently associated with devastating neurologic outcomes, despite with emergent surgical intervention. Here, we presented an example of an intramedullary hemorrhage occurring in a spinal hemangioblastoma, where the patient markedly improved with surgery. Additionally, the appropriate literature was reviewed (including intraoperative video). CASE DESCRIPTION: A 49-year-old female with a 4-year history of tingling in the left lower extremity presented with vomiting, stepwise worsening of bilateral scapular pain, new upper motor neuron signs, and severe sensory loss bilaterally below C4 on the left and T4 on the right. The magnetic resonance imaging demonstrated a well-circumscribed, uniformly enhancing intramedullary tumor at the C2 level with hyperintensity on the T2 study consistent with acute hemorrhage and cord edema. An urgent C2 laminectomy was performed for gross total tumor resection. Intraoperatively, intramedullary hemorrhage was identified anterior to the tumor mass and was confirmed histopathologically. Postoperatively, the patient had no new sensorimotor deficits and fully recovered within two postoperative months. CONCLUSIONS: Patients presenting with acute intramedullary hemorrhage within hemangioblastomas of the spinal cord may demonstrate significant postoperative neurological recovery.

Hypervascular Vestibular Schwannomas: Clinical Characteristics, Angiographical Classification, and Surgical Considerations.

BACKGROUND: There is a rare type of vestibular schwannoma, scarcely discussed in the literature, known as a hypervascular vestibular schwannoma (HVS). OBJECTIVE: To evaluate its biological characteristics, angiographical classification, surgical outcomes, and the significance for surgical consideration, using a large series of this clinical entity. METHODS: The definition for HVS in this study was the tumor stain from the vertebrobasilar system (VBS) in angiography. The authors conducted a retrospective analysis of 36 patients who were angiographically diagnosed with HVS and underwent surgery between 2008 and 2015. Their biological findings and their surgical outcomes were compared with non-HVS subjects. With regard to the tumor feeders and AV shunt, we classified HVS into 5 types. RESULTS: HVS occurred more commonly in younger subjects (mean: 39.4 yr), as a larger solid tumor with multiple flow voids (mean: 34.1 mm), and involved higher levels of cerebrospinal fluid protein (mean: 202 mg/dl) and a higher MIB1-index (mean: 4.3%). The average resection rate for these 36 cases was 95.3%, and recurrence was seen in 6 cases (16.7%). Compared with non-HVS, the extent of tumor resection was significantly lower, and the recurrence rate was significantly higher. Especially in HVS type 2B (the tumor stain is fed by the VBS and the external carotid artery, with an arteriovenous shunt from the VBS), the recurrence-free survival duration was significantly shorter compared with other HVS types and non-HVS, and HVS type 2B exhibited an identifiable risk factor for recurrence. CONCLUSION: HVS have the distinct clinical characteristics compared with those of non-HVS subjects.

Long-Term Patency of Posterior Auricular Artery-Middle Cerebral Artery Bypass for Adult-Onset Moyamoya Disease: Case Report and Review of Literature.

BACKGROUND: Direct extracranial-intracranial (EC-IC) bypass is one of the fundamental techniques to prevent recurrent stroke in patients with adult-onset ischemic moyamoya disease. When the standard superficial temporal artery (STA) cannot be used for a graft, the posterior auricular artery (PAA) can be a potential surrogate graft. CASE DESCRIPTION: In this article, the authors reported a 34-year-old female patient suffering from ischemic moyamoya disease. To widely revascularize the anterior half of the hemisphere, direct double EC-IC bypass was considered beneficial; however, she had only a single-branched STA but had a prominent branch of the PAA. After discussion, a direct double surgical revascularization was successfully performed using a combination of the STA-middle cerebral artery (MCA) and the PAA-MCA bypass. The authors herein reported the detailed surgical technique of the PAA-MCA bypass with an informative video of the actual procedure. To clearly define the feasibility of PAA-MCA bypass, the authors also conducted a literature review, yielding 3 previous articles describing the bypass. CONCLUSION: In conclusion, the PAA becomes a potential donor for EC-IC bypass as long as its diameter is approximately 1.0 mm. Even though the PAA-MCA bypass is not primarily considered in the initial revascularization, it can be useful as a combination bypass with other grafts or as a rescue for recurrent ischemia.

Medical Engineering and Microneurosurgery: Application and Future.

Robotics and medical engineering can convert traditional surgery into digital and scientific procedures. Here, we describe our work to develop microsurgical robotic systems and apply engineering technology to assess microsurgical skills. With the collaboration of neurosurgeons and an engineering team, we have developed two types of microsurgical robotic systems. The first, the deep surgical systems, enable delicate surgical procedures such as vessel suturing in a deep and narrow space. The second type allows for super-fine surgical procedures such as anastomosing artificial vessels of 0.3 mm in diameter. Both systems are constructed with master and slave manipulator robots connected to local area networks. Robotic systems allowed for secure and accurate procedures in a deep surgical field. In cadaveric models, these systems showed a good potential of being useful in actual human surgeries, but mechanical refinements in thickness and durability are necessary for them to be established as clinical systems. The super-fine robotic system made the very intricate surgery possible and will be applied in clinical trials. Another trial included the digitization of surgical technique and scientific analysis of surgical skills. Robotic and human hand motions were analyzed in numerical fashion as we tried to define surgical skillfulness in a digital format. Engineered skill assessment is also feasible and should be useful for microsurgical training. Robotics and medical engineering should bring science into the surgical field and training of surgeons. Active collaboration between medical and engineering teams and academic and industry groups is mandatory to establish such medical systems to improve patient care.

Microsurgical robotic system for the deep surgical field: development of a prototype and feasibility studies in animal and cadaveric models.

OBJECT: To enhance the surgeon's dexterity and maneuverability in the deep surgical field, the authors developed a master-slave microsurgical robotic system. This concept and the results of preliminary experiments are reported in this paper. METHODS: The system has a master control unit, which conveys motion commands in six degrees of freedom (X, Y, and Z directions; rotation; tip flexion; and grasping) to two arms. The slave manipulator has a hanging base with an additional six degrees of freedom; it holds a motorized operating unit with two manipulators (5 mm in diameter, 18 cm in length). The accuracy of the prototype in both shallow and deep surgical fields was compared with routine freehand microsurgery. Closure of a partial arteriotomy and complete end-to-end anastomosis of the carotid artery (CA) in the deep operative field were performed in 20 Wistar rats. Three routine surgical procedures were also performed in cadavers. The accuracy of pointing with the nondominant hand in the deep surgical field was significantly improved through the use of robotics. The authors successfully closed the partial arteriotomy and completely anastomosed the rat CAs in the deep surgical field. The time needed for stitching was significantly shortened over the course of the first 10 rat experiments. The robotic instruments also moved satisfactorily in cadavers, but the manipulators still need to be smaller to fit into the narrow intracranial space. CONCLUSIONS: Computer-controlled surgical manipulation will be an important tool for neurosurgery, and preliminary experiments involving this robotic system demonstrate its promising maneuverability.

Assessing Microneurosurgical Skill with Medico-Engineering Technology.

OBJECTIVES: Most methods currently used to assess surgical skill are rather subjective or not adequate for microneurosurgery. Objective and quantitative microneurosurgical skill assessment systems that are capable of accurate measurements are necessary for the further development of microneurosurgery. METHODS: Infrared optical motion tracking markers, an inertial measurement unit, and strain gauges were mounted on tweezers to measure many parameters related to instrument manipulation. We then recorded the activity of 23 neurosurgeons. The task completion time, tool path, and needle-gripping force were evaluated for three stitches made in an anastomosis of 0.7-mm artificial blood vessels. Videos of the activity were evaluated by three blinded expert surgeons. RESULTS: Surgeons who had recently done many bypass procedures demonstrated better skills. These skilled surgeons performed the anastomosis with in a shorter time, with a shorter tool path, and with a lesser force when extracting the needle. CONCLUSIONS: These results show the potential contribution of the system to microsurgical skill assessment. Quantitative and detailed analysis of surgical tasks helps surgeons better understand the key features of the required skills.

Diagnosis of acute ischemic stroke based on time-to-peak and diffusion-weighted magnetic resonance imaging.

Rapid and accurate diagnosis of the hemodynamics of the brain is essential for the treatment of acute ischemic stroke. This study investigated whether time-to-peak and diffusion-weighted magnetic resonance (MR) imaging are useful for predicting the course of stroke. Fourteen patients with non-lacunar acute ischemic stroke underwent emergent MR imaging within 24 hours from the onset followed by cerebral angiography and xenon-enhanced computed tomography (CT). Serial CT was obtained to monitor changes in the size and nature of the infarct. Volumes of the abnormal lesions demonstrated on time-to-peak (VT) or diffusion-weighted (VD) images were measured, and the ratio of VT to VD was calculated. Based on this ratio, patients were classified into three groups: Group 1 (VT/VD 0.5-1.5, n = 9), Group 2 (VT/VD > 1.5, n = 3), and Group 3 (VT/VD < 0.5, n = 2). The size of the infarct detected as a low-density area on serial CT scans did not change significantly throughout the course in Group 1 patients, but showed enlargement in all three patients in Group 2. Two patients in Group 3 had major trunk occlusion followed by spontaneous reperfusion, and both developed hemorrhagic transformation. Our study showed that classification of ischemic stroke based on the VT/VD ratio was predictive of the time course of the infarct, and may be useful in selecting the initial therapeutic procedure immediately after the onset of stroke.