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Background: For a minimally invasive treatment approach to the anteromedial part of the anterior cranial fossa (ACF), a small incision and craniotomy of the posterolateral part of the ACF are preferable., Method: We described the concept and technique of suprapterional keyhole approach (SPKA), which uses an exoscope and endoscope to treat ACF lesions., Conclusion: The SPKA enables ACF observation from the lateral direction; the endoscope's extended viewing angles enable the observation of the anteromedial part of the ACF, including the bilateral olfactory groove. Facial skin and large scalp incisions are avoided, making this approach efficient for ACF lesions., (© 2024. The Author(s).)

Background: The endoscopic transorbital approach provides a direct access to the medial temporal lobe (MTL). However, when excising a highly vascular tumour, a wider access route that enables the concurrent use of standard neurosurgical instruments with both hands is preferable., Method: We described the concept and technique of the lateral orbital wall approach (LOWA), which comprises orbitotomy and mini-craniotomy to treat MTL lesions using an exoscope and endoscope., Conclusion: The LOWA provides a safe and natural surgical corridor to the MTL and enables 2- or 3-hand surgery. Hence, LOWA can potentially improve safety and efficiency to treat MTL lesions., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system with a poor prognosis and is primarily caused by JC virus (JCV) with a mutation called prototype. We encountered a case of PML with moderate progression and analyzed the mutational patterns of JCV in the cerebrospinal fluid (CSF). A 19-year-old Japanese woman with mild neurological symptoms was diagnosed with combined immunodeficiency following pneumocystis pneumonia. Brain magnetic resonance imaging scan showed multiple brain lesions, and real-time polymerase chain reaction testing detected JCV in the CSF, leading to the diagnosis of PML. The disease course of PML was stable after administration of mefloquine and mirtazapine with immunoglobulin replacement therapy. In the JCV genome cloned from the patient CSF, DNA sequences of the gene encoding the capsid protein (VP1) and the non-coding control region exhibited small mutations. However, they were quite similar to those of the archetype JCV, which persists asymptomatically in healthy individuals. These findings provide insight into the mutational characteristics of JCV in PML with mild symptoms and progression., (© 2021. Journal of NeuroVirology, Inc.)

Background: We present a case series of underwater microvascular decompression (MVD) for hemifacial spasm (HFS) and an evaluation of its feasibility and safety., Methods: This retrospective study was conducted at a single institution and included 20 patients with HFS who underwent underwater MVD between September 2019 and January 2021. Surgery was performed in 3 steps, as follows: exoscopic wound opening (soft tissue, bone, dura, and arachnoid around the cerebellomedullary cistern), underwater endoscopic surgery (decompression of the facial nerve), and exoscopic wound closure. In underwater endoscopic surgery, the surgical field was continuously irrigated with artificial cerebrospinal fluid. Abnormal muscle response and brainstem auditory evoked potentials (BAEPs) were monitored., Results: Neurovascular conflicts were clearly observed in all patients without fogging and soiling of the endoscope lens. HFS was completely relieved in 19 patients (95%). An amplitude reduction of wave V of BAEPs of more than 50% was not observed in any of the cases. In 5 cases (25%), the latency of wave V of BAEPs was prolonged for more than 1.0 ms; these changes completely or near completely returned to baseline values at dural closure in all 5 cases. A postoperative complication of transient facial palsy was observed in 1 patient (5%) during postoperative days 10-30. There were no other complications., Conclusions: Our findings suggest that underwater MVD is a safe and feasible option for the treatment of HFS. However, it did not show advantages over conventional endoscopic MVD when the protective effect on the eighth cranial nerve was evaluated., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)