Vestibular paroxysmia caused by a subarcuate artery: illustrative case.

BACKGROUND: Vestibular paroxysmia is defined by spontaneous, recurrent, short, paroxysmal episodes of vertigo. The authors present a case of vestibular paroxysmia caused by neurovascular compression of the vestibulocochlear nerve due to the subarcuate artery, which was successfully treated with microvascular decompression. OBSERVATIONS: A 46-year-old man first experienced vertigo attacks 5 years earlier. The attacks became more frequent, and left-sided tinnitus developed over the past 4 months, prompting a referral to our hospital. Carbamazepine treatment alleviated symptoms but had to be discontinued due to rash. Brain magnetic resonance imaging and angiography revealed that the left anterior inferior cerebellar artery was pressing on the cisternal segment of the left vestibulocochlear nerve. The authors diagnosed vestibular paroxysmia caused by neurovascular compression and performed microvascular decompression. During the operation, a subarcuate artery was identified as the offending vessel, with a prominent indentation on the vestibulocochlear nerve. The vertigo was completely relieved following surgery. LESSONS: Neurovascular compression of the vestibulocochlear nerve by the subarcuate artery can result in vestibular paroxysmia. https://thejns.org/doi/abs/10.3171/CASE24239.

MAST4 promotes primary ciliary resorption through phosphorylation of Tctex-1.

The primary cilium undergoes cell cycle-dependent assembly and disassembly. Dysregulated ciliary dynamics are associated with several pathological conditions called ciliopathies. Previous studies showed that the localization of phosphorylated Tctex-1 at Thr94 (T94) at the ciliary base critically regulates ciliary resorption by accelerating actin remodeling and ciliary pocket membrane endocytosis. Here, we show that microtubule-associated serine/threonine kinase family member 4 (MAST4) is localized at the primary cilium. Suppressing MAST4 blocks serum-induced ciliary resorption, and overexpressing MAST4 accelerates ciliary resorption. Tctex-1 binds to the kinase domain of MAST4, in which the R503 and D504 residues are key to MAST4-mediated ciliary resorption. The ciliary resorption and the ciliary base localization of phospho-(T94)Tctex-1 are blocked by the knockdown of MAST4 or the expression of the catalytic-inactive site-directed MAST4 mutants. Moreover, MAST4 is required for Cdc42 activation and Rab5-mediated periciliary membrane endocytosis during ciliary resorption. These results support that MAST4 is a novel kinase that regulates ciliary resorption by modulating the ciliary base localization of phospho-(T94)Tctex-1. MAST4 is a potential new target for treating ciliopathies causally by ciliary resorption defects.

Ciliary Assembly/Disassembly Assay in Non-transformed Cell Lines.

The primary cilium is a non-motile sensory organelle whose assembly and disassembly are closely associated with cell cycle progression. The primary cilium is elongated from the basal body in quiescent cells and is resorbed as the cells re-enter the cell cycle. Dysregulation of ciliary dynamics has been linked with ciliopathies and other human diseases. The in vitro serum-stimulated ciliary assembly/disassembly assay has gained popularity in addressing the functions of the protein-of-interest in ciliary dynamics. Here, we describe a well-tested protocol for transfecting human retinal pigment epithelial cells (RPE-1) and performing ciliary assembly/disassembly assays on the transfected cells.