Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) of autoimmune etiology that predominantly affects young adults; it is considered to be mediated by activated T cells and there is evolving evidence of a significant contribution from B cells and cells of the innate immune system. Pathophysiologically, it appears that immune activation attacks the myelin sheath, causing progressive and irreversible axonal degeneration. Current MS phenotypic classifications include relapsing-remitting MS (PRMS), clinically isolated syndrome, radiologically isolated syndrome, primary-progressive MS, and secondary-progressive MS. Clinical relapses in RRMS reflect acute inflammation of the CNS, resulting in specific clinical syndromes, including optic neuritis, myelitis, brainstem/cerebellum syndrome, and supratentorial syndrome. In progressive MS, progression is generally associated with gradual loss of power in the lower limbs, which may be asymmetric, often accompanied by sensory disturbances in the lower limbs, and bladder and bowel symptoms. In addition, chronic progressive brain atrophy is commonly observed in cases of MS. The McDonald diagnostic criteria, recently revised in 2017 revision, are currently widely accepted. Magnetic resonance imaging of the brain and spinal cord is necessary for the diagnosis of MS. The diagnosis of MS remains fundamentally clinical and requires the necessary clinical expertise to demonstrate evidence of dissemination in time and space, and importantly, exclusion of other neurological conditions. Analysis of the cerebrospinal fluid allows evaluation of inflammatory processes circumscribed confined to the CNS and reflects changes in the immunological pattern with progression of the pathology, and is fundamental for the diagnosis and monitoring of MS. Many disease-modifying drugs have shown different levels of efficacy in preventing relapses, accumulation of lesions (as assessed by magnetic resonance imaging), and disability progression.

　Vestibular migraine (VM) and Meniere's disease (MD) are both characterized by recurrent, episodic vertigo. In patients with recurrent vertigo, it is sometimes difficult to differentiate between VM and MD if the vertigo is not associated with migrainous headache or hearing loss.

　In the present study, to differentiate between VM and MD, we analyzed the results of examinations of the peripheral vestibular system; the medical records of 23 patients, including 12 with definite VM and 11 with definite MD, were reviewed retrospectively, with a focus on the results of the caloric test and cervical vestibular evoked myogenic potential (cVEMP) testing.

　The caloric test revealed no statistically significant difference in the incidence of canal paresis between patients with VM and MD; however, the asymmetry ratio (AR) of cVEMP obtained using 500-Hz short-tone burst stimuli was significantly higher in patients with MD than in patients with VM (p=0.04, Fisher's exact probability test). The tuning properties of short-tone burst stimuli of 500Hz and 1,000Hz during cVEMP testing tended to shift to a higher frequency in the affected ears of patients with MD as compared with that in the ears of patients with VM, although the difference was not significant (p=0.12, Welch's t-test). These differences are consistent with the findings of a previously conducted pathological investigation of the temporal bone in patients with MD, which suggested that severe endolymphatic hydrops is observed most frequently in the saccule of the inner ear.

　The present study findings indicate that evaluation of dysfunction of the saccule, especially the AR in cVEMP may be helpful in the differential diagnosis between VM and MD.

　Primary central nervous system lymphoma (PCNSL) is a lymphoma that is confined to the brain and spinal cord. The clinical manifestations vary depending on the site of origin, but the main presenting complaint in most cases is loss of memory.

　In this study, we encountered a case of PCNSL in which the patient presented to the ENT department with the complaints of dizziness and hearing impairment, which led to the diagnosis. At the first visit, there were no neurological findings other than dizziness and hearing impairment, but as the disease progressed, many neurological findings became evident. Since the symptoms of PCNSL progress rapidly, it is necessary to perform detailed examinations, such as imaging tests, at an early stage without overlooking the slightest signs.

　Bow hunter's syndrome is a form of vertebrobasilar insufficiency in which cervical rotation causes mechanical occlusion or stenosis of the vertebrobasilar artery, resulting in various symptoms, including dizziness, vertigo, and/or syncope. We report a case of Bow hunter's syndrome in which cervical rotation caused dizziness and nystagmus.

　A 45-year-old woman presented to our hospital complaining of experiencing vertigo and nausea when twisting her neck. Nystagmus testing using Frenzel goggles revealed nystagmus during right cervical rotation. There was no hearing loss. Magnetic resonance imaging (MRI) showed no evidence of cerebral infarction; however, basi-parallel anatomical scanning MRI revealed arterial dissection in the left vertebral artery more peripherally than beyond the branching off of the posterior inferior cerebellar artery. Cervical ultrasonography and vertebral angiography confirmed that the patient experienced vertigo due to lack of blood flow in the proximal portion of the left vertebral artery when she rotated her neck 90 degrees to the right.

　Neurosurgeons at our institution performed neurosurgical C1-C2 posterior fixation, which led to complete resolution of her symptoms.

　The pathogenesis of Bow hunter's syndrome can take many distinct patterns, and the direction of cervical rotation does not always correspond to the side of the symptoms. To diagnose Bow hunter's syndrome, it is important to positively identify the onset of symptoms during cervical rotation and perform appropriate imaging studies.

　Herein, we report the case of a 76-year-old woman with dural arteriovenous fistula (dAVF) who presented with dizziness. At her first visit to our otolaryngology outpatient clinic, she complained of dizziness and staggering while walking, but there were no obvious symptoms of cranial nerve involvement. She presented with leftward nystagmus under an infrared CCD camera and unconscious left-dominant sensorineural hearing loss.

　Based on the above, she was diagnosed as having probable acute impairment of the inner ear and treated with prednisolone, and anti-motion sickness and antiemetic medications. CT and MRI revealed cerebellar edema and cortical venous ectasia. We referred the patient to the Department of Neurosurgery, and cerebral angiography revealed transverse-sigmoid sinus dAVF, type II according to Borden's classification, fed mainly by the left occipital artery.

　We performed embolization of the left occipital artery 14 days after the patient first visited us. Blood flow through the left occipital artery decreased, but there was only scarce improvement of the cerebellar edema caused by collateral vascular flow. We referred her to a university hospital. 42 days after her first visit, the patient underwent embolization was performed against reflux to the right superior petrosal sinus from residual shunts of the left middle meningeal artery, left ascending pharyngeal artery and left tentorial artery by way of the left sigmoid sinus at the university hospital. The cerebellar edema improved, and the patient was discharged 58 days after the first visit.

　Although this patient never complained of tinnitus, many cases of dAVF complain of pulsatile tinnitus. In cases of type I (Borden's classification) dAVF who do not have cortical venous reflux, the condition is usually not severe, whereas dAVF with cortical venous reflux can be fatal. Careful attention should be paid to the presence of pulsatile tinnitus.

　Machine learning is an algorithm that allows computers to learn from existing data to find patterns and apply the learned results to new data to predict the future. Practical examples include machine translation, speech recognition, dialogue systems, handwriting recognition, facial image recognition, and automated driving. Recent research and applications in the medical field include automated detection of tumors on CT images and endoscopic images.

　The advantages of machine learning are that it can be applied to a wide range of problems and that large amounts of data that can ordinarily not be handled by humans can be processed, as it is more accurate and faster than humans.

　A practical example of machine learning in the field of equilibrium research is the prediction of vestibular disorders from posturography data. We evaluated a dataset from Fujimoto et al. (Otol. Neurotol., 2014), including posturography and vestibular function data and found that machine learning algorithms can be successfully used to predict vestibular dysfunction as identified using caloric testing with the dataset of the center of pressure sway during posturography.

　Some of the points to be considered for practical application of machine learning in the field of vertigo research include the following: clinical data contain many errors, and database errors may occur frequently, the accuracy of clinical examinations should be taken into account, the difference between the acute and chronic phases of disease should be taken into account, and the dizziness symptom varies among cases. In order to achieve better accuracy, a large amount of data is required, and multi-institutional joint research should be considered.