Intracranial neurenteric cysts are relatively rare and almost exclusively benign. Here we present a case of an intracranial neurenteric cyst that was histologically benign in the first surgery and later demonstrated significant growth and intracranial metastasis with malignant transformation. A 47-year-old woman presented with a headache, which had gradually worsened over 1 year. Initial magnetic resonance (MR) images revealed a solitary cystic lesion in the left cerebellopontine angle with significant mass effect. Subtotal resection leaving a small mass strongly adhered to the brainstem was achieved. Histopathological diagnosis was neurenteric cyst with no malignant features. This lesion recurred 4 years after the first surgery in the form of a cystic mass adjacent to the brainstem. In addition, histopathological examination of a specimen from the second surgery revealed malignant transformation. The patient declined to undergo radiation therapy and was conservatively managed. Three years after the second surgery, MR imaging showed recurrence of the solid mass. Although the patient had been treated with subtotal resection and radiation therapy, she died with metastatic masses in the right frontal lobe and cervical cord. A specimen from the third surgery revealed diffuse malignant features similar to mucinous adenocarcinoma. Our case and literature review indicate that, although rare, malignant transformation can occur particularly among intracranial neurentreric cysts. This finding suggests the importance of long-term follow-up for subtotally or partially resected intracranial neurenteric cysts.

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Osteoid osteoma is a benign bone tumor characterized by local pain that typically increases at night. The tumor commonly occurs in the long bones of the lower extremities, and in rare instances in cranial bones. Here we report the case of a 25-year-old man diagnosed with an osteoid osteoma of the right occipital condyle. The patient suffered from severe occipital pain in the 3 years leading up to surgery, and the pain disappeared after surgical resection of the tumor. Due caution must be taken to avoid vertebral artery injury in the surgical approach in this region. An intraoperative navigation guidance system and preoperative analysis using three-dimensional reconstructed computed tomography (CT) images improved the accuracy and safety of the resection. The typical pain in osteoid osteoma is presumed to be associated with prostaglandin E2 secretion. Plasma prostaglandin E2 of this patient was elevated preoperatively and normalized after the operation. This is the first report describing an elevation of plasma prostaglandin E2 before surgical resection followed by a normalization of serum prostaglandin E2 after surgical resection.

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Two cases of exposed titanium mesh occurred after implantation for cranioplasty after repeated procedures for microvascular decompression (MVD). Case 1 was a 62-year-old female who underwent MVD for left hemifacial spasm followed by repair of cerebrospinal fluid leak after the surgery, and Case 2 was a 75-year-old female who underwent MVD twice for right trigeminal neuralgia. Both patients visited our hospital again with complaints of postauricular lesion. Titanium mesh was visible through the operative scar and was successfully removed with no complication in both cases. Both patients were underweight females, and combined with multistep surgery may have contributed to the pathology. The present cases suggest that use of titanium mesh should be avoided for cranioplasty of posterior fossa surgery, especially for repeated procedures.

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Moyamoya disease usually manifests as ischemic events in childhood, and as more severe hemorrhagic events, including intraventricular hemorrhage, in adults. Recently, the indication for neuroendoscopic surgery has been extended to cast-formation intraventricular hematomas. However, detailed information about the use of neuroendoscopic surgery for the treatment of intraventricular hemorrhage associated with moyamoya disease has not been reported. We describe two cases of intraventricular hemorrhage with moyamoya disease; one in a 62-year-old and another in a 33-year-old women who both presented with severe neurological symptoms. Cerebral angiography revealed unilateral moyamoya disease. Neuroendoscopic surgery to remove the intraventricular hematoma was performed via bilateral frontal burr holes in both cases. Abnormal findings in the ventricle were observed only in the affected side and the intact side was normal. Specific findings of neuroendoscopic observation were dilated and tortuous vessels, intersection vessels, black-brown macules in the subependyma, and rattan blind-like (Japanese sudare) bleeding vessels. These characteristic neuroendoscopic findings may be useful for the exact diagnosis and treatment of intraventricular hemorrhage associated with moyamoya disease. Endoscopic evacuation of the ventricular hematoma may be important for intracranial pressure control in patients with intraventricular hemorrhage in adult moyamoya disease.

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The diagnosis of peroneal nerve (PN) entrapment neuropathy (PNEN) is based on clinical symptoms and nerve conduction studies. However, these studies do not always detect PNEN. Our 64-year-old patient suffered persistent left L5 numbness after two lumbar surgeries. Two years before admission to our institute his left leg pain gradually reappeared. When walking, his numbness in the left lower thigh to the dorsum of the foot increased. Electrophysiological testing revealed no conduction block on the PN. To identify the origin of his intermittent symptoms we performed loading of repetitive ankle plantar flexion in the at-rest posture to avoid the lumbar factor. We used this provocation test to check for PNEN because it occurs at a site where the PN passes the soleus- and the peroneus longus muscle (SM, PLM). The symptoms appeared reproducibly within 10 s of loading. PN neurolysis under local anesthesia showed that the PN was strongly compressed by the SM and PLM. This procedure eased his symptoms and he was able to walk without elicitation of numbness and pain upon repetitive ankle plantar flexion. In our case, repetitive plantar flexion elicited the symptoms and this provocation test may be useful to identify PN dynamic entrapment neuropathy as the origin of intermittent claudication.

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