Surgical Concepts and Long-term Outcomes of Thalamic Deep Brain Stimulation in Patients with Severe Tourette Syndrome: A Single-center Experience.

Tourette syndrome (TS) is a developmental neuropsychiatric disorder that is characterized by tic movements. Deep brain stimulation (DBS) may be a treatment option for severe cases refractory to medical and behavioral therapies. In this study, we reviewed the surgical techniques used for DBS in patients with severe TS and its clinical outcomes and sought to determine the optimal surgical procedure and current issues based on our experience and the literature. A total of 14 patients, consisting of 13 men and 1 woman, who underwent centromedian thalamic DBS and were followed up for a mean duration of 2.3 ± 1.0 years, participated in this study. The mean Yale Global Tic Severity Scale severity score significantly improved from 41.4 ± 7.0 at baseline to 19.8 ± 11.4 at 6 months (P = 0.01) and 12.7 ± 6.2 at the last follow-up (P < 0.01). Moreover, the mean Yale Global Tic Severity Scale impairment score significantly improved from 47.1 ± 4.7 at baseline to 23.1 ± 11.1 at 6 months (P < 0.01) and 7.6 ± 2.9 at the last follow-up (P < 0.01). However, there were problems with continuous postoperative monitoring (three cases were lost to follow-up) and surgery-related adverse events, including one case each of lead misplacement and a delayed intracerebral hemorrhage due to severe self-injurious tics. This study aimed to highlight not only the clinical efficacy of DBS for TS but also its challenges. Clinicians should understand the three-dimensional brain anatomy so that they can perform precise surgical procedures, avoid adverse events, and achieve favorable outcomes of DBS for TS.

Asymptomatic cable twisting in a patient with impending Twiddler syndrome detected during deep brain stimulation surgery for Parkinson's disease: A case report.

Background: Deep brain stimulation (DBS) has consistently demonstrated high efficacy and safety in patients with Parkinson's disease. Twiddler's syndrome is a rare occurrence of hardware failure in patients undergoing neuromodulation. We report here a case of subclinical cable twisting jeopardizing Twiddler's syndrome in a patient with Parkinson's disease who underwent DBS surgery targeting the globus pallidus internus (GPI). Case Description: A 70-year-old woman with a 7-year history of Parkinson's disease refractory to medication was referred to our department for treatment of involuntary movements of the left hand and leg. She underwent right GPI DBS implantation. Left GPI DBS implantation was subsequently planned to manage resting tremors that developed in the right leg after the first surgery at around one year after the first surgery. During a routine check-up before the second surgery, we incidentally detected Twiddler's syndrome. The patient showed no neurological deficits in the left extremities, the same as before right GPI DBS. We performed left GPI DBS concomitantly with the revision of the implantable pulse generator and extension wire. Conclusion: Twiddler's syndrome is a rare complication of DBS. Subclinical risk of cable twisting jeopardizing Twiddler's syndrome is rarely detected without clinical indications of hardware failure. Neurosurgeons should be cognizant of and regularly monitor the implanted device in case serious complications occur.

[Various Bypass Surgery:Preoperative Simulation for STA-MCA Bypass].

In STA-MCA bypass surgery, it is important to select the optimal recipient using preoperative simulation to avoid complications. We report a preoperative simulation for STA-MCA bypass using the Brain LAB iPLAN platform®BRAIN LAB)and the 3DCG simulation software GRID®Kompath). Here, we introduce the basics and applications of preoperative simulation for occlusive atherosclerotic lesions and present a target bypass for periventricular anastomosis and peripheral vessels of aneurysms in Moyamoya disease. By creating and visualizing 3D fusion images, the optimal donor and recipient can be selected. Determining the skin incision and extent of craniotomy according to the case is also applicable to the minimally invasive STA-MCA bypass. Preoperative simulations enable accurate pinpoint bypass surgery and prevent complications.

Disappearance of a moyamoya-related distal anterior cerebral artery aneurysm after target bypass revascularization: illustrative case.

BACKGROUND: Aneurysm formation is a complication of moyamoya disease (MMD). Distal anterior cerebral artery (ACA) aneurysms account for approximately 1% of MMD-related aneurysms. We report a case of target bypass for adult patients with MMD who presented with intracranial hemorrhage due to rupture of a distal ACA aneurysm, whose disappearance was confirmed postoperatively. OBSERVATIONS: A 45-year-old woman presented with sudden-onset headache and loss of consciousness. Head computed tomography showed hemorrhage in the genu of the corpus callosum with intraventricular extension. Digital subtraction angiography (DSA) revealed Suzuki stage III MMD and a left A3 segment aneurysm. Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass and STA-ACA target bypass were performed to reduce hemodynamic stress on the left ACA. DSA 6 months after surgery showed patency of both bypasses and disappearance of the aneurysm. At the 20-month follow-up, the patient was asymptomatic and neurologically intact. LESSONS: Bypass revascularization may be an effective treatment to reduce hemodynamic stress and eliminate MMD-related aneurysms.

Repeated coil embolization of traumatic basilar artery pseudoaneurysm accompanied by bilateral traumatic internal carotid artery stenosis following severe head injury in a pediatric patient: A case report and literature review.

Background: Few cases of pediatric traumatic intracranial aneurysms (pTICAs) in the posterior circulation involving the basilar artery (BA) following severe head trauma have been reported. Here, we describe a pediatric case of traumatic BA pseudoaneurysm accompanied by bilateral traumatic internal carotid artery (ICA) stenosis following blunt head trauma. Case Description: A 16-year-old boy presented to our emergency department after being hit by a car. The patient was initially diagnosed with multiple skull base fractures underlying traumatic subarachnoid hemorrhage and left acute epidural hematoma. Seven days following emergency craniectomy, magnetic resonance imaging revealed bilateral ICA stenosis, BA stenosis, and BA pseudoaneurysm. We decided to perform coil embolization, resulting in body filling and a volume embolization ratio of 15.7%. Twenty-eight days after coil embolization, digital subtraction angiography revealed aneurysmal rupture. We performed repeated coil embolization, resulting in body filling and a volume embolization ratio of 20.9%. Conclusion: We reported a pediatric case of traumatic BA pseudoaneurysm accompanied by bilateral traumatic ICA stenosis following a severe head injury treated with repeated coil embolization. Considering the risk of further brain injury due to high incidence of rupture, early vascular survey and appropriate treatment may be the most important prognostic factors in pTICAs.

Presence of intra-aneurysmal thrombi with delayed coil migration after embolization of an aneurysmal subarachnoid hemorrhage: illustrative case.

BACKGROUND: Coil migration is a rare, but notable complication of endovascular treatment. Risk factors include communicating segment aneurysms, aneurysmal shape, and technical factors. Although cerebral blood flow obstruction caused by early coil migration requires urgent coil removal, delayed coil migration is often asymptomatic, making it difficult to determine a treatment strategy. OBSERVATIONS: A 47-year-old woman was referred to the institute with acute-onset headache. She was diagnosed with subarachnoid hemorrhage due to rupture of the right internal carotid artery-posterior communicating artery aneurysm and underwent endovascular coil embolization. Following the procedure, the patient showed no obvious complications; however, 14 days later, images showed coil migration to the distal side, leading to surgical removal. Right frontotemporal craniotomy was performed, and the remaining coil was removed. The aneurysm was clipped again, and blood flow was confirmed. The patient was discharged 12 days after the craniotomy with transient oculomotor nerve palsy. At the 15-month follow-up, there was no aneurysm recurrence and the oculomotor nerve palsy showed improvement. LESSONS: Retrieval of the migrated coil by craniotomy is an effective remedial measure; however, intraoperative complications are common. Early detection, established protocols, and prompt treatment decisions are important for preventing undesirable outcomes.

Case report: isolated trochlear nerve palsy associated with posterior cerebral artery aneurysm.

We describe a case of isolated trochlear nerve palsy caused by an unruptured posterior cerebral artery (PCA) aneurysm in an 82-year-old male who consulted an ophthalmologist after developing diplopia. Magnetic resonance angiography showed a left PCA aneurysm in the ambient cistern, and T2WI showed an aneurysm compressing the left trochlear nerve to the cerebellar tentorium. Digital subtraction angiography revealed that the lesion was located between the left P2a segment. We attributed this isolated trochlear palsy to left PCA unruptured aneurysm pressure. Thus, we performed stent-assisted coil embolization. The aneurysm was obliterated, and trochlear nerve palsy improved completely.

Manual superficial temporal artery compression using a circular plastic material for embolization of meningioma: illustrative case.

BACKGROUND: In meningiomas that occur in the high-convexity region, the superficial temporal artery (STA) frequently feeds the tumor, and when embolizing from the middle meningeal artery (MMA), the embolic material may not reach the tumor vessels because of the pressure gradient resulting from the STA blood flow, resulting in inadequate embolization. In this case, a circular plastic material was used to apply circumferential pressure around the parietal foramen to control blood flow to the tumor. OBSERVATIONS: A 45-year-old male underwent head magnetic resonance imaging that revealed a 2.2-cm meningioma in the right high-convexity region. Preoperative embolization was performed. When N-butyl-2-cyanoacrylate was injected from the right MMA while using a circular plastic material to compress the skin around the parietal foramen through which the bilateral STAs (the tumor feeders) flow, it was able to fully penetrate the tumor vessel and occlude the other feeders in a retrograde manner. The patient underwent tumor removal after embolization uneventfully. LESSONS: Manual compression of the STA using a circular plastic material is useful when the tumor is fed by the STA through the parietal foramen and is also applicable to transarterial embolization of dural arteriovenous fistulas fed by the STA or occipital artery.

Case report: Radiofrequency thalamotomy as palliative care for Holmes tremor in a patient with terminal cancer and cardiac pacemaker.

Background: Herein, we present a case report of a patient with Holmes tremor due to thalamic infarction with end-stage pancreatic cancer who underwent successful computed tomography (CT)-guided ventralis intermedius nucleus (Vim) thalamotomy as palliative care. Case Description: A 78-year-old man with gradually worsening involuntary movements on the left side of his body 2 years after a right thalamic infarction was referred to our institute. He had a history of chronic atrial fibrillation for which he was implanted with a cardiac pacemaker not compatible with magnetic resonance imaging. He also received adjuvant therapy for pancreatic cancer. As the involuntary movements interfered with his daily life, the patient elected for neurosurgical treatment despite having terminal cancer. Although the prognosis for pancreatic cancer was considered to be more than 6 months at the time of surgery, we performed CT-guided Vim thalamotomy under local anesthesia without pulse generator implantation considering the patient's general condition. The involuntary movements of the left side of the body reduced following surgery, thus improving his quality of life (QOL). However, 6 months after thalamotomy, the patient died of pancreatic cancer. Conclusion: Thalamotomy significantly reduced the involuntary movements immediately after the procedure. Therefore, thalamotomy can be performed under local anesthesia without the use of any device and may contribute to the improvement of QOL in terminal patients.

Favorable management of symptomatic cerebellar hemangioblastoma presenting with obstructive hydrocephalus during pregnancy: A case report and literature review.

Background: Cerebellar hemangioblastoma is a highly vascular benign tumor and the growth rate of hemangioblastomas is believed to often accelerate during pregnancy; however, the reason for this rapid increase in size remains poorly understood. There are several case reports of symptomatic hemangioblastoma during pregnancy; however, the favorable management strategy has not been well established. Case Description: A 35-year-old woman, gravida 2 para 1, with no significant medical history presented with vertigo and difficulty walking at around 11 weeks of pregnancy and was referred to our institute at 30 weeks of gestation because of worsening symptoms. Brain magnetic resonance imaging revealed a 5.6 cm cystic lesion with a mural nodule in the right cerebellar hemisphere and the lesion blocked cerebrospinal fluid drainage from the fourth ventricle and brainstem, resulting in obstructive hydrocephalus. After obtaining the patient's consent, a multidisciplinary team consisting of obstetricians and neurosurgeons decided to perform resection of the intracranial lesion following delivery of the fetus by emergency cesarean section in view of the symptoms of increased intracranial pressure. The patient's general condition was confirmed to be stable postoperatively and she was discharged on the 16th day of her hospitalization without any neurological deficits or fetal complications. Conclusion: Urgent tumor resection combined with cesarean section can be planned once fetal lung maturity is confirmed. Most cases of symptomatic hemangioblastoma during pregnancy have an uneventful gestational course and a favorable outcome for both mother and child.

Enlargement of preexisting superficial temporal artery pseudo-aneurysm co-incidental to mask wearing during the Covid-19 pandemic.

The superficial temporal artery (STA) pseudo-aneurysm is usually associated with trauma. We report a unique case of an STA pseudo-aneurysm that developed due to mask wearing during the Covid-19 pandemic. A 70-year-old female presented with a 3-month history of a rapidly growing pseudo-aneurysm of the right STA. Over the past 3 months the patient had been wearing a mask for the prevention of Covid-19. The STA aneurysm was located exactly at a pressure point created by the rubber mask. Therefore, we assumed that an enlargement of the preexisting aneurysm had taken pace due to irritation from the elastic band of the mask. Surgical excision of the aneurysm and reconstruction of the STA using STA-STA bypass were performed. To our knowledge, we here report the first case of an STA pseudo-aneurysm that was potentially affected indirectly by the Covid-19 pandemic. Clinicians should be cautious about the preexisting medical condition that is potentially worsened by mask band compression.

Optimal surgical indications of endoscopic surgery for traumatic acute subdural hematoma in elderly patients based on a single-institution experience.

Recently, treatment of acute subdural hematoma (ASDH) by minimally invasive surgery with endoscopy has been successfully demonstrated. However, few case series are available on this procedure for ASDH, and the surgical indication has not been established. We retrospectively analyzed the data of patients (n = 26) aged 65 years or older who underwent endoscopic surgery (ES) for ASDH at our institution between January 2011 and March 2019. We then evaluated the surgical outcomes and procedure-related complications in patients who underwent ES. The mean hematoma reduction rate was over 90%. Percentage of favorable outcomes at discharge was 69.2% in ES-treated patients. The presence of a skull fracture, subarachnoid hemorrhage, midline shift/subdural hematoma thickness ratio > 1.0, and early surgery were associated with postoperative IPHs in patients who underwent ES or conventional surgery for ASDH. The present study revealed that ES for elderly patients with ASDH is likely to be an efficient and safe procedure when patients are selected appropriately. However, ES is not recommended in patients with significant IPHs on initial CT scan. Additionally, ES should be carefully considered in cases with the factors, where IPHs may progress following surgery.

A Case of Salivary Duct Carcinoma Intracranial Invasion due to Perineural Invasion Through the Facial Nerve.

BACKGROUND: Salivary duct carcinoma (SDC) is a rare parotid tumor that often develops as a rapidly growing mass with a poor prognosis. It has a high rate of distant metastases, sometimes with infiltration along nerves. We describe a case of SDC that originated outside the cranium and extended into the cranium along the path of the facial nerve. CASE DESCRIPTION: A 74-year-old man underwent magnetic resonance imaging at a local hospital, which revealed a tumor in the left internal acoustic canal; the patient was referred to our department. A left facial schwannoma was suspected, and magnetic resonance imaging was performed again 6 months later. Rapid tumor growth was confirmed, and the tumor was resected. The tumor displayed atypical epithelial cells with comedo necrosis and cribriform structure and was diagnosed as SDC. All residual intracranial tumors were removed using the middle fossa approach. The tumor, which was considered to be a primary tumor, was found near the stylomastoid foramen, and it was removed with the parotid gland. Five months after the initial surgery, metastasis to the trigeminal nerve was observed, and this was removed using a retrosigmoid approach, followed by radiation therapy. CONCLUSIONS: All 4 surgical specimens of this case were presented, and the path of tumor progression was examined in detail. Although the primary lesion was small, intracranial invasion along the facial nerve occurred. SDC should be considered as a tumor that can extend into the cranium, even with a small primary lesion.

[Microvascular Decompression to Treat Abducens Nerve Paralysis Caused by Compression of the Anterior Inferior Cerebellar Artery:A Case Report].

Microvascular decompression(MVD)is an effective treatment for hemifacial spasm and trigeminal neuralgia. However, there are few reports regarding its use with abducens nerve palsy. Here, we report the case of a 77-year-old male who presented with diplopia and was admitted to our facility for right abducens nerve palsy. MRI constructive interference in steady-state(CISS)showed that the right anterior inferior cerebellar artery(AICA)was curved in a posterior-superior direction at the beginning of the region of origin, causing compression of the root exit zone of the right abducens nerve. In addition, MRI showed an unruptured fusiform aneurysm(5.3mm×7.1mm)of the vertebral artery(VA)involving the posterior inferior cerebellar artery(PICA). However it was not related to abducens nerve paralysis. The aneurysm was successfully treated with an occipital artery-posterior inferior cerebellar artery(OA-PICA)bypass and clipping of the proximal VA and PICA origin. The position of the offending artery was moved using a Teflon® felt fibrin glue and the retrosigmoid transcondylar fossa approach. The patient recovered from abducens nerve paralysis with no new neurological deficit. We emphasize the importance of choosing an appropriate approach as this increases the possibility of treating abducens nerve paralysis in a timely manner.

[A Case of Meningeal Solitary Fibrous Tumour/Haemangiopericytoma WHO Grade III Metastasized to the Spleen Shortly After Tumor Resection].

Revision of WHO guidelines in 2016 led to the classification of solitary fibrous tumours(SFTs)and haemangiopericytomas(HPCs)as a single tumor entity characterized by NAB2-STAT6 fusion. Standard-of-care treatment involves surgery, but local recurrence and distant metastasis sometimes occur. The average latency to metastasis after surgery is 99 months. A 38-year-old female patient presented with a complaint of headache. An 8×5×2cm lesion showing Gd-T1 enhancement was detected near the superior sagittal sinus. Pathological assessment following resection revealed proliferating, polymorphic, atypical tumor cells with distinct nucleoli in a "patternless pattern." Cellularity was moderate to high, and mitotic figures were observed in 15/10 high power fields. Immunohistochemically, tumor cells tested positive for STAT6, and RT-PCR revealed a NAB2-STAT6 fusion gene(exons 6 and 17, respectively), supporting a diagnosis of SFT/HPC WHO grade III. Despite postoperative radiotherapy, multiple metastases to the spleen were detected 8 months after surgery, and distal pancreatectomy with splenectomy was performed. The pathology of the splenic tumor was similar to that of the intracranial tumor. Recurrent disease in a lymph node was detected 1 month later, and local radiation therapy was administered. The patient died of cancerous peritonitis 5 months later. In this case, exceedingly rapid metastasis to the spleen occurred, despite the administration of vigorous treatment. Here, we review SFT/HPC incidence, treatment, and outcomes to better understand this rare malignancy.

A retrospective evaluation of thalamic targeting for tremor deep brain stimulation using high-resolution anatomical imaging with supplementary fiber tractography.

OBJECTIVES: Deep brain stimulation (DBS) of the ventral intermediate (Vim) thalamic nucleus is used to treat tremors. Here, we identified the Vim nucleus on fast gray matter acquisition T1 inversion recovery (FGATIR) images and delineated the dentate-rubrothalamic tract (DRT) to determine the DBS target. We evaluated whether this method could consistently identify the Vim nucleus by anatomical imaging and fiber tractography. METHODS: We retrospectively reviewed clinical data of patients who underwent unilateral thalamic DBS for severe tremor disorders. We evaluated outcomes at baseline, 6 months and 1 year following intervention, and annually thereafter. We reviewed preoperative planning to determine whether our tractography technique could consistently depict the DRT, and evaluated implanted electrode position by fusing postoperative CT scans to preoperative MR images. RESULTS: Seven patients (three men and four women) were included; preoperative diagnoses included essential tremor (n = 3), Parkinson's (n = 2), and Holmes tremor (n = 2). All patients responded to DBS therapy; motor scores improved at 6-month and last follow-up. The Vim nucleus was successfully identified, as the DRT was depicted in all cases. Of ten active DBS contacts in seven leads, four contacts were located outside of the depicted DRT, and these contacts tended to require higher stimulation intensity. CONCLUSIONS: The Vim nucleus was successfully identified with FGATIR. Our methods may be useful to determine optimal DBS trajectory, and potentially improve outcomes.

Clinicopathological and genetic characteristics associated with brain metastases from lung adenocarcinoma and utility as prognostic factors.

Brain metastases (BM) are common in patients with lung adenocarcinoma, and represent a significant cause of morbidity in the disease. A more comprehensive understanding of the clinicopathological characteristics that serve as prognostic factors for survival in patients with BM from lung adenocarcinoma may aid in informing treatment strategies for this patient population. In the present study, clinicopathological factors, including EGFR mutation status, were evaluated in 59 patients who were diagnosed with BM from lung adenocarcinoma, and underwent BM resection between January 1985 and December 2014 at Fukuoka University Hospital. The most frequent subtype of BM from lung adenocarcinoma was solid adenocarcinoma (57.6%), followed by papillary adenocarcinoma (22.0%) and acinar adenocarcinoma (18.6%). A total of 14 patients (23.7%) exhibited EGFR mutations, which were significantly associated with female sex (9/14, 64.3%), non-smoker status (8/14, 57.1%), BM in the frontal lobes (9/14, 64.3%) and papillary adenocarcinoma (5/14, 35.7%). Statistical analysis revealed a significant association between non-smoker status and BM in the frontal lobes, and more favorable disease prognosis. The results of the present study suggest that histological and genetic analysis of tissue from BM provides information useful for managing treatment of patients with resectable BM arising from lung adenocarcinoma.

An Infratemporal Dermoid Cyst That Expanded the Foramen Ovale: A Case Report.

BACKGROUND: Dermoid cysts are rare tumors usually seen in the midline structure of the brain but rarely arise in the petrous apex and cavernous sinus. There have been very few reports of dermoid cysts arising in the infratemporal fossa, with scarce anatomic descriptions. Here we report the case of a patient with a dermoid cyst in the left infratemporal fossa. CASE DESCRIPTION: The patient was a 43-year-old female with complaints of nonspecific headaches. A computed tomography (CT) scan revealed a cystic lesion measuring 25 × 18 × 15 mm in the left infratemporal fossa that had expanded the foramen ovale. The same lesion was observed as a high-intensity area on T1-weighted magnetic resonance imaging (MRI) with fat saturation. Diffusion-weighted MRI showed no restriction, unlike in cases of epidermoid cysts. A left fronto-temporo-sphenoidal craniotomy with a detachment of the zygoma was performed to approach the lesion. The tumor wall was continuously attached to the dura, although the tumor itself was entirely extradural in location. The V3 branch of the trigeminal nerve was firmly attached around the tumor. The tumor was cystic, and it shrunk after the fatty yellowish contents were suctioned. Complete resection was achieved without complications. A pathological analysis enabled the diagnosis of a dermoid cyst. No tumor recurrences or associated complications were observed at the 1-year follow-up. CONCLUSIONS: Dermoid cysts in the infratemporal fossa are extremely rare. However, tumor resections can be performed safely and efficaciously using anatomically detailed preoperative planning.

Analysis of Evolving Clinicopathological Features of Metastatic Brain Tumors Over 30 Years of Surgical Management.

We reviewed 232 cases, in which patients underwent surgical resection and histopathological diagnosis of metastatic brain tumor between 1985 and 2014. We analyzed trends in clinicopathological changes present over three decades in a single institution. The most frequent site of metastatic tumors was the frontal lobe. The average patient age and the percentage of female patients increased over the 30-year study period. The most frequent primary cancer was lung cancer, followed by breast cancer; these were the top two primary cancer types over the three decades. However, use of chemotherapy and radiotherapy as standard treatments for postoperative treatment of metastatic brain tumors has increased over the past 20 years. Development of novel, targeted treatments for these cancer types have created new tools for use in the clinical care of patients with metastatic brain tumors. Incorporation of these tools in a multimodal approach is critical in contemporary management of metastatic brain tumors.

Unilateral Trans-cerebellomedullary Fissure Approach for Occipital Artery to Posterior Inferior Cerebellar Artery Bypass during Aneurysmal Surgery.

Occipital artery (OA) to the posterior inferior cerebellar artery (PICA) bypass is indispensable for the management of complex aneurysms of the PICA that cannot be reconstructed with surgical clipping or coil embolization. Although OA-PICA bypass is a comparatively standard procedure, the bypass is difficult to perform in some cases because of the location and situation of the PICA. We describe the usefulness of the unilateral trans-cerebellomedullary fissure (CMF) approach for OA-PICA bypass. Thirty patients with aneurysms in the vertebral artery (VA) or PICA were treated using OA-PICA bypasses between 2010 and 2015. Among them, the unilateral trans-CMF approach was used for OA-PICA anastomosis in 13 patients. The surgical procedures performed on and the medical records of all the patients were retrospectively reviewed. The unilateral trans-CMF approach was performed for two reasons depending on the PICA location or situation: either because the caudal loop could not be used as a recipient artery because of arterial dissection (3 patients) or because the tonsillo-medullary segment that was located in the upper part of the CMF did not have a caudal loop that was large enough (10 patients). The trans-CMF approach provided a good operative field for the OA-PICA bypass and the anastomosis were successfully performed in all patients. When the recipient artery was located in the upper part of the CMF, the unilateral trans-cerebello-medullary fissure approach provided a sufficient operative field for OA-PICA anastomosis.