Pathophysiology of vertigo/dizziness can be understood by eye deviation (nystagmus). In benign paroxysmal positional vertigo, eye deviation of causative semicircular canal stimulation is directly observed. In other peripheral vestibular disorders, eye deviation results from the sum of unilateral all semicircular canal disorders. The central vestibular pathway is controlled by the cerebellum. Thus, in vertigo/dizziness of central origin, not only eye deviation due to impairment of the central vestibular pathway but also deviation due to disinhibition of the pathway from the cerebellum is observed. The cerebellar control on the central vestibular pathway also plays an important role in vestibular compensation. When treating vertigo/dizziness, it is necessary to understand the pathophysiology of the vertigo/dizziness, to set the treatment target based on the pathophysiology, and to intervene for the target.

A 71-year-old, right-handed woman was admitted to our hospital due to a sudden difficulty with conversation. On admission, she was alert, but had a euphoric mood, disorientation, and a disturbance of recent memory. Her speech was fluent. Her repetition and auditory word cognition were excellent, but she had a slight difficulty with naming visual objects. She frequently showed word-finding difficulty and irrelevant paraphasia during free conversation and a word fluency task. Her irrelevant paraphasia was observed more frequently when she was asked to explain her outbreak of anger at the hospital, i.e., it was situation-dependent. She also had anosognosia. MRI showed an infarct in the territory of the left tuberothalamic artery. Single-photon emission computed tomography revealed low-uptake lesions in the left thalamus and orbital frontal, medial frontal, and medial temporal lobes. The patient was diagnosed with non-aphasic misnaming. The clinical characteristics of patients with non-aphasic misnaming in the literature were reviewed. All of the patients with non-aphasic misnaming had word-finding difficulty and irrelevant paraphasia. Additionally, they had either emotional disturbance or anosognosia.

We report a patient with bilateral hemispheric lesions caused by two episodes of cerebral infarction who exhibited conduction aphasia with unique jargon. The patient was an 84-year-old, right-handed man. Beginning after the second episode of cerebral infarction (defined as the time of symptom onset), neologistic jargon and an iterative pattern of phonemic variation became prominent, whereas phonological paraphasia and conduite d’approche were observed in the patient’s overall speech. Therefore, the aphasia was characterized by the combination of conduction aphasia and neologistic jargon. At 27 months after symptom onset, the neologisms and iterative pattern of phonemic variation had disappeared, but a wide variety of phonological paraphasia and conduite d’approche persisted, clarifying the pathological features of the conduction aphasia experienced by this patient. The conduction theory (Kertesz et al., 1970) provides a convincing explanation for the mechanism of the onset of neologisms in the present case. Thus, we propose the existence of a symptomatic relationship between neologisms and phonological paraphasia.

A 35-year-old male developed sensory abnormality of peripheral limbs and oral cavity after prior infection with diarrhea and cold symptoms. Hyperrhinolalia, nasopharyngeal reflux, double vision, and wobbling in walking rapidly progressed. Neurological examination revealed palatoplegia, omnidirectional ophthalmoplegia, hyperreflexia, sensory disturbance of extremities, and truncal and limb ataxia due to decreased deep sensation. A peripheral nerve conduction study found a slight decrease in sensory nerve action potential of the median nerve and a decrease in F wave frequency of the median nerve. Serum IgM-CMV antibody was positive on admission. After IVIg therapy, palatoplegia and ataxia markedly improved. In this case, GalNAc-GD1a and GM2 antibodies, which are often detected after CMV infection, were positive in addition to the GT1a and GQ1b antibodies, and it was assumed that these findings were associated with the palatoplegia, which is included in cranial nerve palsy. Pathophysiologically, the present case is considered to be an overlap with acute oropharyngeal palsy (AOP), which is a rare subtype of Guillain-Barre syndrome, and Fisher syndrome (FS). The clinical aspects of the present case suggest a continuous spectrum between AOP and FS.

A 43-year-old woman with a history of tick bite in the mountains in Hokkaido presented with a fever of 39°C, headache, and nausea. Cerebrospinal fluid findings indicated meningitis. On day 3 after admission, she presented with restlessness, disturbance of consciousness, and ataxic breathing, indicative of encephalitis. We administered steroid pulse therapy, tracheal intubation, and a respirator. Her symptoms improved gradually and she was able to breathe without the respirator on day 10 after admission. She was discharged on day 24 after admission with no sequelae. This is the fifth reported case of tick-borne encephalitis in Japan. In the previous four cases, the patients died or suffered severe sequelae. This is the first case without any sequelae in Japan.

We report a case of a 60-year-old man who presented with symptoms of memory loss, gait disorder, and sluggish movement. We considered both Parkinson’s disease and multiple system atrophy as possible diagnoses and consequently hospitalized the patient owing to the worsening symptoms and the development of consciousness disorder. During the course of the disease, dementia, loss of consciousness, and movement disorders worsened rapidly within one year after admission, and the patient eventually developed mutism. The significant clinical characteristics of our case included no myoclonus and involuntary tremors in the extremities. There was no periodic synchronous discharge on electro­encephalography and cranial MRI with diffusion-weighted images showed no high-intensity findings in cortex. Prion protein genetic analysis identified four repeated insertional mutations in the octapeptide repeat (OPR) region, and the patient was diagnosed with inherited Creutzfeldt–Jakob disease. Cases of OPR insertional mutations are a few in Japan and occur in about 10% of population in Europe. Creutzfeldt–Jakob disease with OPR insertional mutation shows various clinical manifestations and atypical findings on electroencephalography and cranial MRI. Diagnosing for Creutzfeldt–Jakob disease with OPR insertional mutation is important in Prion protein genetic analysis.

A 61-year-old man was admitted to our hospital due to cerebral infarction in the pons and the right putamen. On admission (day 3 from symptom onset), laboratory testing showed a white blood cell count of 13,100/μl with hypereosinophilia of 3,734/μl. As deep vein thrombosis was detected on contrast-enhanced CT, we started anticoagulation therapy. There were no cardio-embolic sources, including right-to-left shunt, but eosinophil infiltration was found in biopsy specimens of the gastric mucosa. These findings allowed us to diagnose multiple perforator infarction due to idiopathic hypereosinophilic syndrome (idiopathic HES). After the administration of oral prednisolone was started on day 10, his hypereosinophilia rapidly improved, and no recurrence of deep perforator infarction occurred other than a symptomatic infarction in the left putamen at day 19. There are a few reports of idiopathic HES with multiple infarctions developing in deep perforator regions. The current case suggests that idiopathic HES could cause multiple cerebral infarction restricted to deep perforator areas.

A 86-year-old woman with left hemiparesis was admitted to our hospital. When visiting to our hospital, hemichorea appeared on her left extremities in an ambulance. She also had mild disturbance of consciousness, spatial disorientation, and sensory disturbance. Blood biochemical studies revealed mild renal failure. DWI MRI showed hyperintensities in the postcentral gyrus and a posterior part of the insula in the right hemisphere, but no signal changes in FLAIR. No lesions were detected in the basal ganglia. The DWI-FLAIR mismatch suggested acute cerebral infarction, and we performed intravenous thrombolysis therapy. Her neurological symptoms including hemichorea gradually improved, and she was finally discharged on foot. Two conspicuous points of the present patient are the sensory cortical infarction and an association with renal failure. In this patient, the sensory cortical infarction must produce chorea even though sensory cortical lesions rarely caused chorea. The associated renal dysfunction may play some role in the production of chorea. The double-crash of cerebral infarction and metabolic abnormality (renal dysfunction) may cause hemichorea which is rarely seen in patients with cerebral infarction of the sensory cortex and insula with no metabolic abnormalities.

There have been a few reports on Dipeptidyl peptidase (DPP)-4 inhibitor-induced dropped head syndrome. However, there has been no known report on temporal changes in MRI findings. The patient described here was a 63-year-old man who was prescribed oral sitagliptin (50 mg/day) in February 2019. He experienced a dropped head from mid-January 2020, and in early April that year, he was admitted to our hospital for further evaluation. Weakness of the cervical extensor muscles (MMT 3) was noted, and MRI findings showed that the posterior cervical muscle group was hyperintense on short inversion time inversion recovery (STIR). We suspected sitagliptin to be the cause of his dropped head and discontinued it. On the 10th day of admission, his posture improved to the median position. One month after discontinuation of sitagliptin, MRI findings showed an improvement in the STIR hyperintensity of the posterior cervical muscle. In conclusion, if the initiation of a DPP-4 inhibitor results in dropped head syndrome, discontinuation of the drug should be considered.