A technique for reconstruction of a giant extracranial internal carotid artery aneurysm: A technical note.

Background: Surgery is effective for extracranial internal carotid artery (EICA) aneurysms. However, the risk of cranial nerve injury associated with surgical repair, such as graft-assisted resection and extracranial-intracranial bypass techniques, is relatively high. Here, we report two cases of surgical treatment for EICA aneurysms and describe the surgical techniques and strategies to avoid cranial nerve injury. Methods: Two patients presented to our facility with an increasing cervical pulsatile mass and no neurological symptoms. Angiography showed a large aneurysm in the cervical internal carotid artery. Surgical treatment was performed to prevent rupture of the aneurysm. In both patients, the aneurysm was strongly attached to the vagus nerve. The aneurysm and vagus nerve were carefully dissected using a low-power bipolar (20 Malis; 3 watts), leaving connective tissue on the vagus nerve side. Results: The aneurysm was detached from the vagus nerve without injury. Based on intraoperative findings, one patient underwent clipping, and the other underwent aneurysmectomy and primary closure for aneurysm obliteration and angioplasty. Both patients were discharged without any cranial nerve dysfunction. Conclusion: The selection of a strategy based on intraoperative findings and low-power bipolar cutting is important for the treatment of extracranial carotid artery aneurysms to preserve cranial nerves.

Frontal Sinus Mucosa Bacteriological Features: Evaluation after Unintentional Opening in Neurosurgery.

Objectives The bacteriological features of the frontal sinus mucosa may impose significant complications in neurosurgery, when breached unintentionally. This study aimed to investigate the bacterial flora in patients undergoing frontal craniotomy for cerebrovascular substrate surgery. Design This is a single-center prospective study. Setting When mucosal laceration occurred, the patients underwent frontal sinus reconstruction with mucosa reconstruction, preserving the nasofrontal duct. Participants We enrolled eight consecutive patients who underwent bifrontal craniotomy associated with frontal sinus mucosa laceration. Main Outcome Measures A portion of the mucosa was extracted during the reconstructive procedure and was sent for microbiological analysis. Results None of the patients presented with the bacterial flora in the mucosal cultures. No patient experienced postoperative cerebrospinal fluid leakage or meningitis. One patient with a clinical history of chronic maxillary sinusitis presented with a subcutaneous abscess around the forehead at 9 months postoperatively. The patient rapidly recovered after receiving oral administration of antibiotics. Conclusions Our findings demonstrated that the frontal sinuses were maintained in an aseptic environment in all cases. The results may encourage the development and wider use of transfrontal sinus approaches.

A Case of Microguidewire and Neuroform Atlas Stent Entanglement Resulting in Extraction Difficulty.

Objective: The trans-cell technique in stent-assisted coil embolization is a common treatment method for intracranial aneurysm. However, despite the frequency of its use, reports discussing its complications and their management are few. We describe a case of stent and microguidewire entanglement, which could not be removed, during treatment using the trans-cell technique. We discuss the mechanism of the entanglement and its management. Case Presentation: A woman in her 40s was found to have an unruptured cerebral aneurysm with a maximum diameter of 5.9 mm located in the paraclinodal anterior process of the left internal carotid artery during a close examination of a headache. The aneurysm had an irregular shape and wide neck. Stent-assisted coil embolization was planned. Initially, the coil was embolized using a jailing technique, but the microcatheter was pushed out of the aneurysm during embolization. Thus, we attempted to switch to a trans-cell technique. However, during the process, the stent and microguidewire became entangled and could not be removed. Finally, when the stent slipped off, the entanglement was resolved and the microguidewire was retrieved. Fortunately, the patient was discharged home without postoperative complications. Conclusion: Once a stent and a microguidewire become entangled, safely releasing them is difficult. Thus, it is important to avoid this scenario from occurring.

Asymptomatic subarachnoid hemorrhage following carotid endarterectomy: illustrative case.

BACKGROUND: Carotid endarterectomy (CEA) and carotid artery stenting are common surgical interventions for internal carotid artery stenosis. Cerebral hyperperfusion syndrome (CHS) is a well-known complication of both procedures that can lead to intracranial hemorrhage and worsen clinical outcomes. Here, the authors report a rare case of non-aneurysmal subarachnoid hemorrhage (SAH) following CEA and review the relevant literature. OBSERVATIONS: A 70-year-old woman with hypertension and diabetes presented with progressive visual loss in the right eye and was diagnosed with ocular ischemic syndrome. Imaging revealed severe right cervical carotid artery stenosis. CEA was performed with no complications. Postoperatively, the patient's blood pressure was tightly controlled, with no evidence of CHS. However, an asymptomatic SAH was detected on postoperative day 7. Careful observation and blood pressure control were maintained. Since follow-up magnetic resonance imaging (MRI) showed no enlarging of the SAH and the patient was asymptomatic, she was discharged on postoperative day 15 with a modified Rankin scale score of 0. LESSONS: This case highlights the potential occurrence of non-aneurysmal SAH as a rare complication of CEA, even in asymptomatic patients. Repeated postoperative MRI is necessary to detect such complications. It is crucial to carefully control blood pressure after CEA regardless of symptoms.

Ischemic stroke in a young adult with a known epileptogenic arteriovenous malformation: illustrative case.

BACKGROUND: Brain arteriovenous malformations (AVMs) usually manifest as hemorrhages or seizures. They rarely present with ischemic symptoms, especially in young patients. We present a case of an epileptogenic AVM that led to cerebral infarction due to paradoxical embolic occlusion of the middle cerebral artery (MCA) involving the main feeder of the lesion. OBSERVATIONS: A 35-year-old male had been suffering from AVM-associated epilepsy for 10 years and was scheduled for surgery. He suddenly developed right-sided hemiconvulsions followed by hemiparalysis and impaired consciousness. Computed tomography revealed no intracerebral hemorrhage, and symptoms were initially thought to indicate epilepsy and Todd's palsy. Because of his prolonged symptoms, he underwent magnetic resonance imaging, which revealed a large cerebral infarction due to occlusion of the MCA involving the main feeder of the AVM. The patient underwent AVM resection, and the partially thrombosed nidus was completely removed. Histopathological investigation revealed a fresh thrombus in totally occluded nonarteriosclerotic feeders. He had no atrial fibrillation; however, subsequent transesophageal echocardiography revealed a patent foramen ovale, suggesting a paradoxical embolism. LESSONS: This case serves as a reminder that AVMs can present with considerable variability. Acute cerebral infarction should be considered a possible mechanism of seizures, even in patients with epileptogenic AVM.

A case of infectious intracranial aneurysm that formed and ruptured within a few days after occlusion of the proximal middle cerebral artery by infective endocarditis.

Background: Embolic cerebral infarction and infectious intracranial aneurysms (IIAs) are well-known central nervous system complications of infective endocarditis (IE). In this report, we describe a rare case of cerebral infarction caused by the occlusion of the M2 inferior trunk due to IE, followed by the rapid formation and rupture of IIA. Case Description: A 66-year-old woman was admitted to the hospital with a diagnosis of IE and embolic cerebral infarction after being brought to the emergency department with a 2-day history of fever and difficulty walking. After admission, she was immediately started on antibiotic therapy. Three days later, the patient suddenly became unconscious, and a head computed tomography (CT) scan showed massive cerebral hemorrhage and subarachnoid hemorrhage. Contrast-enhanced CT showed a 13-mm large aneurysm in the left middle cerebral artery (MCA) bifurcation. An emergency craniotomy was performed, and intraoperative findings revealed a pseudoaneurysm at the origin of the M2 superior trunk. Clipping was considered difficult, so trapping and internal decompression were performed. The patient died on the 11th day after surgery due to the worsening of her general condition. The pathology of the excised aneurysm was consistent with a pseudoaneurysm. Conclusion: IE may cause occlusion of the proximal MCA and rapid formation and rupture of IIA. It should be noted that the location of IIA may be a short distance away from the occlusion site.

Retrieval of N-Butyl-2-Cyanoacrylate Glue Migrated to the Vertebral Artery via Dangerous Anastomosis, Using the Stent-Retriever Aspiration Technique, during Dural Arteriovenous Fistula Embolization: A Case Report.

Objective: We report a case of accidental N-butyl-2-cyanoacrylate (NBCA) glue migration into the vertebral artery (VA) via dangerous anastomosis during transarterial embolization (TAE) for transverse sinus (TS)-dural arteriovenous fistula (DAVF), which was rescued by mechanical retrieval using a stent retriever and aspiration devices. Case Presentation: A 49-year-old right-handed female patient was admitted to our hospital with motor aphasia. MRI revealed congestion in the left temporal and occipital lobes, involving a small hemorrhage. DSA revealed a DAVF complicated by a sinus thrombus in the left TS. The DAVF was mostly fed by the left occipital artery (OA) and drained into the cortical veins of the temporal and occipital lobes through the patent part of the sinus. TAE was performed via the left OA with low-concentration NBCA. However, NBCA glue migrated into the left VA through a dangerous anastomosis, and a left VA angiogram revealed severe VA stenosis and floating NBCA glue. There was a fragile attachment of the NBCA glue to the arterial inner wall; therefore, we successfully retrieved the NBCA glue with a stent retriever and aspiration devices without complications. Finally, TAE was performed using another feeder, and the DAVF was completely obliterated. Conclusion: TAE using NBCA is useful for the treatment of DAVF; however, it should be noted that there is a risk of migration via potential anastomotic routes. Low-concentration NBCA glue can be retrieved using these devices in limited cases.

Multiple large vessel occlusions resulting in vessel perforation in single pass of mechanical thrombectomy with stent retriever.

Mechanical thrombectomy (MT) is a highly effective treatment for acute ischemic stroke, and hemorrhagic complications caused by vessel injury are rare. However, there is no evidence regarding the efficacy of MT for multiple large vessel occlusion or its procedural strategy. Herein, we report a case of MT with a stent retriever for multiple large vessel occlusion in the internal carotid artery and middle cerebral artery M1 distal, which resulted in vessel perforation in a single pass. A 79-year-old woman underwent MT for internal carotid artery occlusion, and multiple large vessel occlusion was observed on digital subtraction angiography. A longer and larger stent retriever was selected for thrombus retrieval in a single pass. Immediately after retrieval, digital subtraction angiography revealed internal carotid artery recanalization. Then, extravasation was observed from the M1 distal occlusion. Treatment was interrupted after hemostasis was confirmed. Nevertheless, rebleeding occurred after 4 hours. Emergency trapping was performed, and vessel perforation of >1 mm was observed. When retrieving a thrombus in a single pass with a stent retriever for multiple large vessel occlusion, vessel perforation may occur if the device is selected according to the diameter of the proximal occluded vessel. Based on the type of device, even a single pass may result in vessel perforation. Although aggressive MT intervention should be performed for multiple large vessel occlusion, a device that is appropriate for the pathological condition must be selected.

High-Flow Bypass for Ruptured Aneurysms at Non-branching Sites of the Middle Cerebral Artery: A Case Report.

Small cerebral aneurysms that occur at non-branching sites are generally considered to have extremely weak aneurysm walls or a pseudoaneurysm formed by a thrombus. Since conventional clipping and coil embolization are difficult and high-risk, trapping with bypass has been considered the preferred treatment method. The aim of this study is to investigate a case of trapping with high-flow bypass for a ruptured aneurysm at non-branching sites of the middle cerebral artery (MCA). In this study, the CT results indicated subarachnoid hemorrhage, while the CT angiography (CTA) results showed a small aneurysm at the non-branching site of the MCA M1 segment. Moreover, the intraoperative digital subtraction angiography (DSA) results strongly suggested a pseudoaneurysm. The aneurysm was judged to be a pseudoaneurysm over the rupture site of the true aneurysm sac. Coil embolization was performed, but the treatment was interrupted as the aneurysm completely disappeared during the procedure. However, based on the magnetic resonance angiography findings, the aneurysm reappeared on day five and became enlarged. Thus, trapping with high-flow bypass was performed on day 15 and the patient was cured. Owing to the unusual and noteworthy course of this case, trapping with high-flow bypass was considered to be the safest and most reliable first-choice treatment procedure for pseudoaneurysm at non-branching sites of the MCA.

Association of antithrombotic therapy with postoperative rebleeding in patients with cerebral amyloid angiopathy.

BACKGROUND: Cerebral amyloid angiopathy is a common cause of subcortical hemorrhage in older adults. Although open hematoma removal may be performed for severe subcortical hemorrhage, its safety in patients with cerebral amyloid angiopathy has not been established, and postoperative rebleeding may occur. Therefore, this study aimed to investigate factors associated with postoperative rebleeding. METHODS: Out of 145 consecutive patients who had undergone craniotomy for surgical removal of subcortical intracerebral hemorrhage between April 2010 and August 2019 at a single institution in Japan, we examined 109 patients with subcortical hemorrhage who met the inclusion criteria. After excluding 30 patients whose tissue samples were unsuitable for the study, the final study cohort comprised 79 patients. RESULTS: Of the 79 patients, 50 (63%) were diagnosed with cerebral amyloid angiopathy (cerebral amyloid angiopathy group) and 29 (37%) were not diagnosed with noncerebral amyloid angiopathy (noncerebral amyloid angiopathy group). Postoperative rebleeding occurred in 12 patients (24%) in the cerebral amyloid angiopathy group and in 2 patients (7%) in the noncerebral amyloid angiopathy group. Preoperative prothrombin time-international normalized ratio and intraoperative bleeding volume were significantly associated with postoperative rebleeding in the cerebral amyloid angiopathy group (odds ratio = 42.4, 95% confidence interval = 1.14-1578; p = 0.042 and odds ratio = 1.005, 95% confidence interval = 1.001-1.008; p = 0.007, respectively). CONCLUSIONS: Patients with cerebral amyloid angiopathy-related cerebral hemorrhage who are receiving antithrombotic therapy, particularly warfarin therapy, are at a high risk of postoperative rebleeding. TRIAL REGISTRATION: Registry and Registration Number of the study: 19-220, 2019/12/23, retrospectively registered.

Case of effective suction to secure the true lumen for acute occlusion after carotid endarterectomy.

During or following carotid endarterectomy, dissection and occlusion of the internal carotid artery can occur. In cases of stenosis or almost complete occlusion, recanalization is relatively easy; however, in cases of complete occlusion, advancing a guidewire into the true lumen may be challenging. Few reports on how to address this problem have been published. Here, we report a case of suction-enabled advancement of the wire into the true lumen during endovascular treatment of an acute occlusion of the internal carotid artery after carotid endarterectomy. An 80-year-old man underwent carotid endarterectomy; the next morning, he exhibited aphasia and right-sided paralysis, and magnetic resonance images showed left cerebral infarction and left internal carotid artery occlusion. The patient was transferred to our hospital for recanalization. Imaging with contrast material showed that the left internal carotid artery was completely occluded. During recanalization, futile attempts were made to advance the wire into the true lumen. The occlusion was aspirated, and angiography then showed an inflow of contrast material into the vessel, which indicated slight distal widening; this widening allowed the wire to move into the true lumen. The occlusion extended distally, and 2 stents were placed over the entire lesion. Good recanalization was eventually achieved.

Location of hemorrhage with nontraumatic acute subdural hematoma due to ruptured microaneurysm.

BACKGROUND: Nontraumatic acute subdural hematoma (ASDH) may be caused by rupture of a microaneurysm of a cortical artery. In some cases, microaneurysms may have been caused by earlier trauma. Although it is difficult to detect microaneurysms on contrast-enhanced computed tomography (CT) angiography or digital subtraction angiography, it may be suspected based on the plain CT scan results and the clinical course. CASE DESCRIPTION: We experienced three cases presumed to be ASDH due to rupture of a microaneurysm. Plain CT scan showed that the midline shift was smaller than the hematoma thickness, and we judged from the clinical course that there was no trauma immediately before the onset. All three patients had decreased consciousness after arrival and underwent craniotomy for hematoma removal. The source of hemorrhage was in the distal part of the cortical artery, and a microaneurysm was found. In one case, histopathological examination was performed, and traumatic pseudoaneurysm was diagnosed. The postoperative course was good in all three cases. CONCLUSION: If nontraumatic ASDH is suspected, the source of hemorrhage may be located more distally to the middle cerebral artery than in traumatic ASDH; hence, extensive craniotomy is required to search for the location of hemorrhage.

Development of Valve Reversal After Lumboperitoneal Shunt Construction.

OBJECTIVE: The current study aimed to assess the risk factors and preventive measures for valve inversion after lumboperitoneal shunt (LPS) construction. METHODS: The medical records of patients who were admitted to Mito Brain Heart Center from July 2015 to October 2018 were retrospectively analyzed. Next, clinical and neuroimaging data were collected from electronic medical charts and operative notes. The cause of valve reversal was investigated. In addition, a simulated shunt device was established and the efficacy of countermeasures was evaluated. RESULTS: The mean age of the participants was 69.3 (range: 46-88) years, and there were 15 men and 22 women. In total, 20 and 17 patients presented with secondary and idiopathic normal pressure hydrocephalus, respectively. Further, 8 patients had valve reversal. CONCLUSIONS: The distance between the valve and spinous process was found to be significantly correlated with valve reversal. However, the condition can be prevented by fixing the tube at the nuchal ligament.

Clinical Characteristics of Ruptured Intracranial Aneurysm in Patients with Multiple Intracranial Aneurysms.

OBJECTIVE: It is difficult to correctly identify the ruptured aneurysm in patients with multiple intracranial aneurysms. Here, we investigated the clinical characteristics of ruptured intracranial aneurysms in such patients. METHODS: We retrospectively analyzed 361 patients who underwent microsurgical clipping of ruptured intracranial aneurysms at our institution from 2012 to 2018. Patients' age, sex, Fisher group, World Federation of Neurosurgical Societies grade, size (neck width, depth, maximum diameter), location, and shape of intracranial aneurysm, and hemorrhage pattern on admission were reviewed. RESULTS: In total, 266 patients (74%) had single intracranial aneurysms and 95 (26%) had multiple intracranial aneurysms. Eighty-nine of the 95 multiple intracranial aneurysms (94%) had irregular shape (P < 0.01). The median aspect ratios of ruptured and unruptured intracranial aneurysms were 2.2 ± 1.1 and 1.0 ± 0.4, respectively (P < 0.01). Twelve of 95 patients (13%) had ruptured intracranial aneurysms that were smaller than unruptured intracranial aneurysms. Among the 12 patients, the aspect ratios of ruptured intracranial aneurysms were greater than those of unruptured intracranial aneurysms (P < 0.01). Regarding morphologic characteristics, aspect ratio, maximum size, and irregular shape could be the useful predictive factors, but the greatest aspect ratio among patients with multiple aneurysms was the most predictive of an intracranial aneurysm rupture, after adjustment for aneurysmal size (adjusted odds ratio 217.82; 95% confidence interval 56.41-841.08). CONCLUSIONS: The results of this study indicate that the aspect ratio is the most predictive factor of a ruptured intracranial aneurysm in patients with multiple intracranial aneurysms.

Emergency embolectomy for acute middle cerebral artery occlusion with chronic common carotid artery occlusion.

Occurrence of acute middle cerebral artery occlusion with common carotid artery occlusion is rare, and its treatment may be complicated. If the approach route cannot be secured because of carotid artery occlusion, endovascular embolectomy may not be indicated. The best treatment approach for such cases remains controversial. A woman in her 70s was transferred to our hospital in ambulance following a sudden onset of dysarthria and left hemiparesis. Magnetic resonance imaging revealed an ischemic lesion in the right basal ganglia and occlusion of the right common carotid and intracranial middle cerebral arteries. Emergency embolectomy was performed for acute middle cerebral artery occlusion. Postoperative magnetic resonance imaging revealed complete recovery of the right middle cerebral artery blood flow. Emergency embolectomy can effectively treat acute middle cerebral artery occlusion with common carotid artery occlusion.

Preoperative risk assessment for predicting the opening of mastoid air cells in lateral suboccipital craniotomy for microvascular decompression.

OBJECTIVE: Opening of mastoid air cells (MACs), a complication of lateral suboccipital craniotomy for microvascular decompression (MVD), might cause cerebrospinal fluid (CSF) leakage and meningitis. Only a few studies have investigated the association of degree of MAC development and actual opening of MACs. The present study focused on preoperative risk assessment for predicting the opening of MACs. PATIENTS AND METHODS: The study included 204 consecutive patients who underwent MVD at our hospital between January 2014 and December 2018. We retrospectively collected clinical and neuroimaging data from electronic medical charts and discharge summaries. MACs were classified into four types according to neuroimaging data. Postoperative computed tomography (CT) was used to assess patients with and without CSF leakage into MACs. RESULTS: No CSF leakage was observed into types 1 and 2 MACs, but it was noted in 14 of 46 patients (30 %) with type 3 and 44 of 58 patients (76 %) with type 4 MACs. Opening of MACs during surgery could not be recognized in 33 (57 %). CSF rhinorrhea was noted in 1 of the 58 patients with CSF leakage into MACs and meningitis was not noted. CONCLUSION: Patients with types 3 and 4 MACs have a high risk of CSF leakage. Complete prevention of mild symptoms, such as ear obstruction, is challenging even if opened MACs are sealed, but serious complications, such as CSF rhinorrhea and meningitis, can be avoided. For cases in which preoperative CT reveals a high risk of opening of MACs, preventive closure should be performed.

Rupture immediately after growth of unruptured intracranial aneurysms during follow-up.

BACKGROUND: The annual rupture rate of small unruptured intracranial aneurysms (UIAs) <5 mm is generally low; further, small UIAs are often treated conservatively. While the growth of aneurysms during follow-up is associated with a high risk of rupture, the urgency for surgical treatment of asymptomatic enlarged UIAs remains controversial. We experienced two patients in whom UIAs ruptured shortly after asymptomatic growth during follow-up. CASE DESCRIPTION: A 1-mm right middle cerebral artery aneurysm was incidentally found in a 63-year-old woman. Preventive surgery was planned because the aneurysm grew rapidly; however, the aneurysm ruptured preoperatively. A 68-year-old woman had a small (4 mm) aneurysm at the left internal carotid-posterior communicating artery. The aneurysm grew rapidly after many years. Several hours after magnetic resonance imaging was performed, she presented to the hospital with loss of consciousness, and a diagnosis of subarachnoid hemorrhage due to the ruptured aneurysm was made. CONCLUSION: UIAs that rapidly increase during follow-up may be regarded as impending ruptured aneurysms.

Clinical and neuropathologic analysis of intracerebral hemorrhage in patients with cerebral amyloid angiopathy.

OBJECTIVE: To evaluate the clinical and histopathological features of elderly patients with subcortical intracerebral hemorrhage (ICH), and to analyze the presence of cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) type pathologic changes using amyloid beta (Aß) and tau immunohistochemistry. PATIENTS AND METHODS: We retrospectively analyzed cases satisfying the Boston criteria for CAA among patients with subcortical hemorrhage who underwent surgical removal by craniotomy at our hospital. Surgical specimens were subjected to hematoxylin and eosin (HE) staining as well as immunostaining. RESULTS: A total of 54 patients were included in this study, with a mean age of 74.5 years (range: 72.5-76.5 years, 95% confidence interval [CI]; 51% female). Of these 54 patients, 31 (57%) were hypertensive, 18 (33%) were undergoing antithrombotic therapy, and 12 (22%) had dementia. Strong immunoreactivity for Aß40 in the cerebral vessels was observed in 30 patients (55.6%), and among these, 27 patients (90%) also showed strong immunoreactivity for Aß42. Among the 54 patients, 25 (46%) exhibited AD characteristics, including Aß-positive senile plaques and AT8-positive neurons. Multivariate analysis revealed that strong Aß40 immunoreactivity in the cerebral vessels was associated with older patients, females, lack of high blood pressure, and the presence of AT8-positive neurons. CONCLUSION: CAA patients with strong Aß40 deposition in the cerebral vessels were associated with subcortical hemorrhage in our cohort. Future studies should investigate the pathomechanism of ICH in individuals with CAA.

Atypical findings of perineural cysts on postmyelographic computed tomography: a case report of intermittent intercostal neuralgia caused by thoracic perineural cysts.

BACKGROUND: Perineural cysts are sometimes found incidentally with magnetic resonance imaging, and clinical symptoms requiring treatment are rare. Perineural cysts typically exhibit delayed filling with contrast medium on myelography, which is one of the criteria used by Tarlov to distinguish perineural cysts from meningeal diverticula. We present a case of multiple thoracolumbar perineural cysts, one of which was considered the cause of intermittent intercostal neuralgia with atypical findings on postmyelographic computed tomography seen as selective filling of contrast medium. CASE PRESENTATION: A 61-year-old woman presented with intermittent pain on her left chest wall with distribution of the pain corresponding to the T10 dermatome. Magnetic resonance imaging showed multiple thoracolumbar perineural cysts with the largest located at the left T10 nerve root. On postmyelographic computed tomography immediately after contrast medium injection, the largest cyst and another at left T9 showed selective filling of contrast medium, suggesting that inflow of cerebrospinal fluid to the cyst exceeded outflow. Three hours after the injection, the intensity of the cysts was similar to the intensity of the thecal sac, and by the next day, contrast enhancement was undetectable. The patient was treated with an intercostal nerve block at T10, and the pain subsided. However, after 9 months of observation, the neuralgia recurred, and the nerve block was repeated with good effect. There was no recurrence 22 months after the last nerve block. CONCLUSIONS: We concluded that intermittent elevation of cerebrospinal fluid pressure in the cyst caused the neuralgia because of an imbalance between cerebrospinal fluid inflow and outflow, and repeated intercostal nerve blocks resolved the neuralgia. Our case demonstrates the mechanism of cyst expansion.