Kiyotaka Nakamagoe

Clinical, neuropathological, and molecular study in two families with spinocerebellar ataxia type 6 (SCA6)

To clarify the clinical, neuropathological, and molecular characteristics of spinocerebellar ataxia type 6 (SCA6), two unrelated Japanese families with SCA6 were studied. A clinical feature of the two families was late onset “pure” cerebellar ataxia. Pathologically, three SCA6 brains consistently showed Purkinje cell dominant cortical cerebellar degeneration. Morphometric analysis showed that loss of the cerebellar granule cells and inferior olivary neurons were very mild compared with the severity of Purkinje cell loss. There was no obvious ubiquitin immunoreactive nuclear inclusions. All affected patients had identical expanded alleles, and the expansion was also homogeneously distributed throughout the brain without mosaicism. The present study showed that SCA6 is characterised by Purkinje cell dominant cortical cerebellar degeneration, highly stable transmission of the CAG repeat expansion, and lack of ubiquitin immunoreactive nuclear inclusions.

The immunoreceptor adapter protein DAP12 suppresses B lymphocyte–driven adaptive immune responses

Human and mouse B cells lacking functional DAP12 are hyperresponsive, and DAP12 works with MAIR-II (CD300d) to negatively regulate B cell activity.

LC3, an autophagosome marker, is expressed on oligodendrocytes in Nasu-Hakola disease brains.

BackgroundNasu-Hakola disease (NHD) is a rare autosomal recessive disorder characterized by sclerosing leukoencephalopathy and multifocal bone cysts, caused by a loss-of-function mutation of either DAP12 or TREM2. TREM2 and DAP12 constitute a receptor/adaptor signaling complex expressed exclusively on osteoclasts, dendritic cells, macrophages, and microglia. Neuropathologically, NHD exhibits profound loss of myelin and accumulation of axonal spheroids, accompanied by intense gliosis accentuated in the white matter of the frontal and temporal lobes. At present, the molecular mechanism responsible for development of leukoencephalopathy in NHD brains remains totally unknown.MethodsBy immunohistochemistry, we studied the expression of microtubule-associated protein 1 light chain 3 (LC3), an autophagosome marker, in 5 NHD and 12 control brains.ResultsIn all NHD brains, Nogo-A-positive, CNPase-positive oligodendrocytes surviving in the non-demyelinated white matter intensely expressed LC3. They also expressed ubiquitin, ubiquilin-1, and histone deacetylase 6 (HDAC6) but did not express Beclin 1 or sequestosome 1 (p62). Substantial numbers of axonal spheroids were also labeled with LC3 in NHD brains. In contrast, none of oligodendrocytes expressed LC3 in control brains. Furthermore, surviving oligodendrocytes located at the demyelinated lesion edge of multiple sclerosis (MS) did not express LC3, whereas infiltrating Iba1-positive macrophages and microglia intensely expressed LC3 in MS lesions.ConclusionsThese results propose a novel hypothesis that aberrant regulation of autophagy might induce oligodendrogliopathy causative of leukoencephalopathy in NHD brains.

Sequential imaging analysis using MIBG scintigraphy revealed progressive degeneration of cardiac sympathetic nerve in Parkinson’s disease

Background:  Metaiodobenzylguanidine (MIBG) cardiac scintigraphy was used to differentiate Parkinson’s disease (PD) with Lewy body pathology from other degenerative parkinsonisms. MIBG cardiac scintigraphy demonstrates the extent of degeneration of myocardial post‐ganglionic sympathetic nerves in patients with PD. Because of its specificity for Lewy body (LB) pathology, MIBG scan might also be useful biomarker for the neurodegeneration attributed to PD. To estimate the utility of the imaging technique as a biomarker, we conducted sequential imaging analysis and power analysis.

Early vestibular dysfunction in Machado-Joseph disease detected by caloric test

The selective vulnerability of distinct neuronal structures is a major feature of Machado-Joseph disease (MJD), also known as spinocerebellar ataxia 3 (SCA3). Vestibular dysfunction is known to be a symptom of MJD, but little is known about precisely when the vestibular system becomes impaired. Using a caloric test, we evaluated vestibular function in 2 MJD patients. One developed the initial symptom 1 year before evaluation, and the other 3 years before evaluation. Neither demonstrated a bilateral response in electronystagmography using ice-cold water irrigation, indicating severe vestibular disturbance. These results suggest that vestibular dysfunction is a symptom that develops very early in MJD and may contribute to unsteady gait as the initial symptom. The vestibular system thus appears to be one of the structures most vulnerable to MJD.

Downbeat nystagmus associated with damage to the medial longitudinal fasciculus of the pons: A vestibular balance control mechanism via the lower brainstem paramedian tract neurons

The paramedian tract (PMT) neurons, a group of neurons associated with eye movement that project into the cerebellar flocculus, are present in or near the medial longitudinal fasciculus (MLF) in the paramedian region of the lower brainstem. A 66-year-old man with multiple sclerosis in whom downbeat nystagmus appeared along with right MLF syndrome due to a unilateral pontomedullary lesion is described. In light of these findings, a possible schema for the vestibular balance control mechanism circuit of the PMT neurons via the flocculus is presented. Damage to the PMT neurons impaired the elective inhibitory control mechanism of the anterior semicircular canal neural pathway by the flocculus. This resulted in the appearance of anterior semicircular canal-dominant vestibular imbalance and the formation of downbeat nystagmus. From the pathogenesis of this vertical vestibular nystagmus, the action of the PMT neurons in the vestibular eye movement neuronal pathway to maintain vestibular balance was conjectured to be as follows. PMT neurons transmit vestibular information from the anterior semicircular canals to the cerebellum, forming a cerebellum/brainstem feedback loop. Vestibular information from that loop is integrated in the cerebellum, inhibiting only the anterior semicircular canal neuronal pathway via the flocculus and controlling vestibular balance.

Downbeat nystagmus due to a paramedian medullary lesion

Cell groups of the paramedian tract, which are located in the paramedian region of the lower brainstem, are eye-movement-related neurons that project to the cerebellar flocculus. Their inactivation produces downbeat nystagmus, which resembles eye movement disorders resulting from lesions of the cerebellar flocculus in animal experiments. Therefore, paramedian tract cells are assumed to fulfill an important function in ocular movement control, such as gaze-holding and maintaining vestibular balance. This paper presents a 50-year-old female who manifested downbeat nystagmus due to damage to the paramedian tract cells caused by a localized ischemic lesion in the medulla oblongata. We found that a paramedian medullary lesion-induced nystagmus, similar to that observed following floccular lesions, clearly indicates that a subgroup of paramedian tract cells projecting to the flocculus was impaired. This finding has important implications in considering a brainstem-cerebellar feedback loop involved in vestibulo-oculomotor controls, such as vestibular balance. Although there have been a few reports of downbeat nystagmus caused by lesions in the midline region of the lower brainstem, to our knowledge none report the occurrence of nystagmus due to a strictly localized medullar lesion, such as the one described here.

Magnetic resonance images of herpes zoster myelitis presenting with Brown-Séquard syndrome.

A 32-YEAR-OLD RIGHThanded woman was febrile at 39°C for 3 consecutive days, after which she developed a rash accompanied by blisters on the lips and nasal cavity and an abnormal sensation in the peripheral parts of the right lower extremity. Eight days after the onset of neurological abnormalities, the salient neurological features were diminished sensation to pain and temperature on the right side below the T4 dermatome; diminished sensation to pain, temperature, and touch on the left side of the T3 dermatome; loss of touch sensibility on the left side below the T4 dermatome; and incomplete paresis of the left leg. Based on these neurological findings, she was diagnosed with Brown-Séquard syndrome. Magnetic resonance imaging showed a left-dominant, highsignal lesion (Figure 1, A and B) or a gadolinium-enhanced lesion on the left side (Figure 2, A and B) in the spine, particularly at the first and second thoracic vertebrae. Although results of cerebrospinal fluid testing showed that both the cell count and protein level were within the reference range, it revealed Human herpesvirus 3 (varicella-zoster virus) DNA in the spinal fluid using polymerase chain reaction, leading to the diagnosis of herpes zoster myelitis. Combined therapy with steroid pulse and intravenous acyclovir was performed. After 1 week, muscle power of her left iliopsoas and quadriceps increased from 3 and 4 to 5 and 5, respectively, according to manual muscle testing, and she could walk independently without the aid of a stick. After 1 month, bilateral abnormal sensation levels moved down to the T6 dermatome, and the appearance of the lesion on magnetic resonance imaging was reduced. Sensory dissociation, left hyperreflexia, and left positive Babinski signs remained after 3 months. Throughout the course of her disease, no abnormalities in bladder control or deep sensation (eg, position and vibration) were observed.

Vestibular Function Impairment in Alzheimer's Disease.

BACKGROUND Falls and fractures due to impaired balance in patients with Alzheimers disease (AD) have an adverse effect on the clinical course of the disease. OBJECTIVE To evaluate balance impairment in AD from the viewpoint of vestibular functional impairment. METHODS The subjects were 12 patients with AD, 12 dementia-free elderly adults, and 12 younger adults. Vestibular function was assessed using a stepping test, caloric nystagmus, and a visual suppression (VS) test. RESULTS The stepping test was abnormal in 9 of the 12 patients in the AD group. An abnormal stepping test was not associated with self-reported dizziness or tendency to fall. Significant VS abnormalities were present in the AD group. The suppression rate of VS was lower in AD patients with either a tendency to fall or constructional apraxia than in AD patients without either. The velocity of the rapid phase of caloric nystagmus before the VS test was similar in the AD group and the elderly control group. Significant abnormalities of both caloric nystagmus and VS were not present in either the elderly or the younger control groups. CONCLUSION AD could involve impairments in the vestibular control of balance. The VS test is useful for assessing the tendency to fall in AD. Impairment of VS in AD might arise from cerebral vestibular cortex impairment rather than comorbid peripheral vestibular disorders.

Thunderclap headache without hypertension in a patient with pheochromocytoma

Pheochromocytoma is a well known, catecholamine-producing tumor characterized by hypertension, headache, hyperglycemia, hypermetabolism, and hyperhydrosis. Approximately 65% of cases of pheochromocytoma were shown to be associated with hypertension. A case of pheochromocytoma that presented with thunderclap headache (TCH) and palpitations is reported. The patient never showed hypertension during the course of the disease. Paroxysmal headache and palpitations led to the identification of the underlying condition, and the final diagnosis was confirmed by histopathological examination of a surgical specimen. Pheochromocytoma should be identified as a less common although important cause of TCH. In addition, due to its lack of utility in identifying this disorder, negative cranial imaging may impede further investigation of extracranial lesions that may be the cause of a patient’s headache. According to the International Classification of Headache Disorders (ICHD)-II, headache attributed to pheochromocytoma usually develops concomitantly with an abrupt increase in blood pressure. In our case, however, hypertension was never observed, even when the patient was symptomatic. This is the first report of a case of pheochromocytoma with TCH without hypertension.