First evidence of tick-borne encephalitis (TBE) outside of Hokkaido Island in Japan.

Tick-borne encephalitis (TBE) is an infection of the central nervous system caused by the tick-borne encephalitis virus (TBEV). TBE is endemic in parts of Europe and Asia. TBEV is transmitted to humans primarily by Ixodes ticks. There have been 5 TBE cases identified in Japan, all on the northern island of Hokkaido. Rodents with TBEV antibodies and Ixodes ticks have been identified throughout Japan, indicating that TBEV infection might be undiagnosed in Japan. Residual serum and cerebrospinal fluid (CSF) collected in 2010-2021 from 520 patients ≥1 year-of-age previously hospitalized with encephalitis or meningitis of unknown etiology at 15 hospitals (including 13 hospitals outside of Hokkaido) were screened by ELISA for TBEV IgG and IgM antibodies; TBEV infection was confirmed by the gold standard neutralization test. Residual serum was available from 331 (63.6%) patients and CSF from 430 (82.6%) patients; both serum and CSF were available from 189 (36.3%). Two patients were TBE cases: a female aged 61 years hospitalized for 104 days in Oita (2000 km south of Hokkaido) and a male aged 24 years hospitalized for 11 days in Tokyo (1200 km south of Hokkaido). Retrospective testing also identified a previous TBEV infection in a female aged 45 years hospitalized for 12 days in Okayama (1700 km south of Hokkaido). TBEV infection should be considered as a potential cause of encephalitis or meningitis in Japan. TBE cases are likely undiagnosed in Japan, including outside of Hokkaido, due to limited clinical awareness and lack of availability of TBE diagnostic tests.

[A case of hypothyroidism displaying "dropped head" syndrome].

We describe a patient with hypothyroidism displaying "dropped head" syndrome. A 50-year-old man visited our clinic because he was unable to hold his head in the natural position. He had weakness and hypertrophy of the neck extensor muscles. Tendon reflexes were diminished or absent in all limbs. Mounding phenomena were observed in the bilateral upper extremities. Blood biochemical analysis revealed hypothyroidism, hyperlipidemia, and elevated levels of muscle-derived enzymes. Magnetic resonance imaging (MRI) of the neck demonstrated swelling and hyperintensity of the neck extensor muscles on T2-weighted images. The result of biopsy of the right biceps brachii muscle suggested mild atrophy of type 2 fibers. The diameters of the muscle fibers exhibited mild variation. No inflammatory changes were observed. We diagnosed hin as having "dropped head" syndrome due to hypothyroidism. Administration of thyroid hormone agent gradually improved his condition, and he became able to hold his head in the natural position. Levels of muscle-derived enzymes normalized and his hyperlipidemia remitted. Neck MRI also revealed improvement. Our findings suggest that hypothyroidism should be considered in the differential diagnosis of "dropped head" syndrome, although only a few cases like ours have been reported.

[A case presenting with trochlear nerve palsy and segmental sensory disturbance due to circumscribed midbrain and upper pontine hemorrhage].

We describe a patient presenting with trochlear nerve palsy and segmental sensory disturbance due to circumscribed mesencephalic hemorrhage. A 36-year-old man with no past illness visited our hospital complaining of sudden onset of diplopia, dysesthesia of the left face and upper extremity, and acuphenes of the left ear. Neurological examination revealed left trochlear nerve palsy and segmental sensory disturbance of the left side almost above T11 level. Pain and temperature sensation were disturbed, but vibration, joint position, graphesthesia, kinesthesia, and discrimination sensation were spared. Magnetic resonance imaging of the head, performed 7 days after onset, revealed acute to subacute phase hemorrhage at the right inferior colliculus. No abnormalities were identified on cerebral angiography. Symptoms gradually improved with conservative therapy. After about ten weeks, diplopia disappeared and area of sensory disturbance was reduced (disturbance of pain sensation reduced to about T4 level, temperature sensation to about T9). Segmental sensory disturbance usually accompanies spinal cord lesion. However, several cases of similar symptoms following cerebrovascular disease of the brainstem have been reported. Conversely, some reports have indicated that trochlear nerve palsy due to midbrain hemorrhage accompanies sensory disturbance contralateral to the lesion. The nature of sensory disturbance is thus variable. The present case suggests that segmental sensory disturbance might accompany trochlear nerve palsy caused by hemorrhage of the inferior colliculus, as intramedullary fibers of the trochlear nerve and spinothalamic tract are located nearby and somatotopy of the spinothalamic tract is preserved even at the level of the midbrain.

[A case of Sjögren's syndrome with subacute transverse myelitis as the initial manifestation].

We report a case of subacute transverse myelitis associated with Sjögren's syndrome free of xerosis. A 62-year-old man was admitted due to dysesthesia of both lower extremities and the left trunk, weakness of the left leg, and urinary disturbance. Neurological examination showed myelopathy at the Th7 level. CSF had increased protein (82 mg/dl) and IgG (23.4 mg/dl) and IgG index (1.03) but an almost normal cell count (7/mm3). T2-weighted MRI showed a high signal intensity lesion at the sixth and seventh thoracic levels. Although he was free of xerosis, typical sialographic findings, as well as the presence of anti-SSA antibody, are consistent with the diagnostic criteria for Sjögren's syndrome decided by the Japanese research group on Sjögren's syndrome. The patient was treated with prednisolone, 60 mg/day, which completely cured his muscle weakness and difficulty in walking, and sensory disturbance was gradually alleviated. Spinal MRI detected a marked reduction in the size of T2-weighted high signal intensity lesion during prednisolone treatment. In Western countries, central nervous system complications are reported in up to 20% of Sjögren's syndrome patients, but myelopathy is a very rare condition. Only 12 cases, including ours, have been reported. The clinical manifestations of myelopathy in Sjögren's syndrome include acute or subacute transverse myelitis (6 cases, including ours), chronic progressive myelopathies (2 cases.), relapsing and remitting cord syndromes (4 cases) and Brown-Séquard syndrome (none). Ten patients were women. In 9 of 12 cases there were sicca symptoms. The level of the myelopathies in 6 of 10 cases was between the third to eighth thoracic level, consistent with the region vulnerable to ischemia. Eight patients were treated successfully with steroids. We speculate that ischemia due to vasculitis is important in the genesis of myelopathy associated with Sjögren's syndrome. In the case of myelopathy, especially in the thoracic cord, it is necessary to look for evidence of Sjögren's syndrome even when xerosis is unremarkable.