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Among ruptured intracranial aneurysms, aneurysms of the vertebral artery(VA) and posterior inferior cerebellar artery(PICA) are relatively rare, and they exhibit distinct characteristics. These include: 1) a high frequency of diverse aneurysmal morphologies, such as fusiform or dissecting aneurysms; 2) proximity to the lower cranial nerves; 3) the presence of perforators to the medulla oblongata; and, 4) obstruction to the surgical approach by specific bony structures, such as the occipital condyle and jugular tubercle. Consequently, these aneurysms often require interventions that are more complex than simple clipping or coiling, which is typical for anterior circulation aneurysms. Interventions include skull base techniques such as the far-lateral approach and revascularization procedures such as occipital artery(OA)-PICA bypass. Despite these complexities, the rarity of these aneurysms and the recent advancements in endovascular procedures pose challenges for young neurosurgeons in acquiring adequate microsurgical experience. This narrative review addresses the clinical features of VA and PICA aneurysms, the history and variations in the lateral suboccipital approach for these aneurysms, and several bypass techniques for reconstructing the PICA. Lastly, we illustrate our current microsurgical practices through a case presentation accompanied by a surgical video showcasing both the far-lateral approach and the OA-PICA bypass.

Metronidazole is a widely used antibiotic against anaerobic bacteria and protozoa. We report two cases of metronidazole-induced encephalopathy(MIE)during treatment of a brain abscess with metronidazole. The patients developed mental disturbance, and brain MRI showed reversible signals on DWI, FLAIR, and T2. Case 1: A 48-year-old woman was admitted to our hospital with a cerebellar abscess. We initiated treatment with oral metronidazole. After taking the medication, she developed mental disturbance, and her brain MRI showed a hyperintensity within the corpus callosum. We suspected metronidazole toxicity and discontinued metronidazole treatment. The symptoms resolved rapidly within a week, and the hyperintensity on the MRI disappeared. Case 2: A 22-year-old man was admitted to our hospital with a brain abscess. We initiated treatment with oral metronidazole. On day 38, he developed mental disturbance, and his MRI showed hyperintensities within the bilateral dentate nuclei and corpus callosum. These symptoms were consistent with MIE. After cessation of metronidazole, his symptoms and abnormal MRI signals completely disappeared.

Resolution of acute epidural hematoma (AEDH) usually takes several weeks. The authors present an infantile case of AEDH that rapidly decreased within a day and review the literature. A 7-month-old boy fell from a height of approximately one meter and sustained a head injury. On presentation, a skull fracture in the right temporoparietal region was found and a small AEDH was observed on computed tomography (CT) 1 hr after the injury. He was transferred to our institute because of growing AEDH, shown by CT images taken 3 hr after the injury. We decided to treat him conservatively as he did not exhibit any neurological deficits on admission. CT images 24hr after the injury showed significant reduction of the AEDH. There was also an increase in the subcutaneous hematoma. Follow-up CT images did not show enlargement of the AEDH. The patient was discharged with no neurological deficits 3 days after admission. Rapid resolution of the AEDH might have been due to transmigration of the hematoma into the epicranial layer through the fracture gap.

Reversible cerebral vasoconstriction syndrome(RCVS)is characterized by severe headache and diffuse segmental constriction of cerebral arteries that resolves spontaneously within a few months. Although manifestations of stroke are not included in diagnostic criteria of RCVS, it is known that some cases may be associated with stroke, including intracerebral hemorrhage, subarachnoid hemorrhage, or cerebral infarction. We present three cases of RCVS associated with various types of stroke, and then review the literature. Case 1:A 49-year-old woman presented with a headache followed by left hemiparesis and dysarthria. One month before the onset, she was transfused for severe anemia caused by uterus myoma. CT images revealed intracerebral hemorrhages in the right putamen and right occipital lobe. Angiography revealed multiple segmental constrictions of the cerebral arteries. One month after the onset, these vasoconstrictions improved spontaneously. Case 2:A postpartum 38-year-old woman who had a history of migraine presented with thunderclap headache. Imaging revealed a focal subarachnoid hemorrhage in the right postcentral sulcus and segmental vasoconstriction of the right middle cerebral artery. One week after the onset, this vasoconstriction improved spontaneously. Case 3:A 32-year-old woman who had a history of migraine presented with headache followed by left homonymous hemianopsia. Imaging revealed a cerebral infarction of the right occipital lobe and multiple constrictions of the right posterior cerebral artery. These vasoconstrictions gradually improved spontaneously.

Although a large number of patients with unruptured middle cerebral artery (MCA) aneurysms (AN) have been treated by surgical clipping in Japan, there has yet been no comprehensive study investigating the surgical risks based on a quantitative evaluation of the extensive existing body of patient records. This systematic review was conducted to determine morbidity of the procedure by performing a meta-analysis of the literature. The authors used a PubMed and J-stage search from 2000 to 2011 for studies containing the surgical clipping of the unruptured MCA AN. There were 21 articles, containing a total 1,323 cases of unruptured AN with morbidity specifically located in the MCA. 54 cases indicated significant neurological deficits for a morbidity rate of 4.1% (95% CI; 3.0-5.1). A limited number of studies disclosed an incremental increase in morbidity with the size of the aneurysm. Smaller MCA AN (7±3 mm) presented a lower morbidity of 1.48%, whereas giant MCA AN (>25 mm) corresponded with a higher morbidity of 27.8%. Factors consistently associated with high morbidity included incorporated MCA branches, plaque at the neck of the AN, an unclippable configuration, and M1 superior wall AN. Complex aneurysms required a wide array of intracranial bypass procedures, yielding morbidity of 23.4% (95% CI; 20.9-25.9). This is the first systematic review and quantitative meta-analysis of the surgical complications related to unruptured MCA AN.

In Japan, a large number of surgical treatments for unruptured intracranial aneurysms have been performed. On the other hands, it is known that surgical treatment for unruptured intracranial aneurysms is the most frequent source of lawsuits in the neurosurgical field. Neurosurgeons have the duty to disclose all risks and consequences of a proposed surgical procedure to each patient. Moreover, precise knowledge of surgical risks would be helpful in preventing complications from occurring. However, it is almost impossible that a single surgeon or an institute have experiences with all possible surgical complications because there is limitation of the number of surgery. In this review series, we attempted an exhaustive bibliographic survey of the possible surgical complications including exceptional ones, and then, determined the frequency of each complications as far as possible quantitatively. In this paper, we focused on the complications of surgical treatment for anterior cerebral artery aneurysms.

Fungal infection is an increasing problem in patients treated with intensive chemotherapy or immunosuppressive therapy. Of these, invasive aspergillosis or mucormycosis on rare occasions, infiltrate the internal carotid artery (ICA) by contiguous spread from an infected paranasal sinus. Here, we report three cases of ICA infiltration secondary to the fungal infections of the paranasal sinus. All cases developed orbital apex syndrome when the lesion spread to the orbital apex or cavernous sinus, and aggressive progression led to ICA invasion causing life-threatening cerebral infarction or hemorrhage. In this case report, we describe the aggressive clinical course of the fungal ICA invasion from the paranasal sinus, and then discuss the clinical feature, diagnostic methods, and current treatment of intracranial fungal infection.

A 9-year-old boy presented a painful right painful parietal mass that rapidly enlarged within a month. He had no other symptom of infection or malignancy. Laboratory findings were normal. Plain skull X ray demonstrated a "punched-out" lesion in the right parietal bone. Magnetic resonance (MR) imaging revealed a 4 x 4 x 3 cm mass centered in the right parietal bone which was enhanced after administration of a contrast material. In addition, as well as the mass region, the pericranial soft tissue was densely enhanced. The parietal bone mass was soft and successfully removed. Histological examination disclosed Langerhans cell histiocytosis (LCH) infiltrating the temporal muscle. MR imaging is useful for diagnosis of LCH of the skull with soft tissue involvement.