Hideo Yamanouchi

Abnormal cortical excitability in Rett syndrome

Visual and somatosensory evoked potentials (VEPs and SEPs) were studied in 9 patients with Rett syndrome and compared with those in 6 patients with photosensitive progressive myoclonus epilepsy (PPME). In Rett syndrome, a giant III-IV amplitude of VEPs was present in 8 patients, although none exhibited giant II-III amplitudes. Four of 6 patients with Rett syndrome who demonstrated giant SEPs did not have a C reflex. Conversely, the patients with PPME demonstrated giant II-III and III-IV amplitudes in VEPs, and giant SEPs with concurrent positive C reflexes. It is concluded that the mechanism of altered cortical excitability in Rett syndrome is different from that in PPME.

An autopsy case of ornithine transcarbamylase deficiency.

We present an autopsy case of ornithine transcarbamylase (OTC) deficiency with grumose degeneration in the dentate nucleus of the cerebellum. The patient had intractable neonatal convulsions and hyperammonemia from the 3rd day after birth. Diagnosis of OTC deficiency was made based on null activity of the enzyme and four-base deletions in exon 9 of the OTC gene. Death was due to sepsis as well as disseminated intravascular coagulation at 1 year and 2 months of age. Neuropathology showed multiple cystic changes and ulegyria in the bilateral frontal and parietal lobes. Multiple cysts were associated with the region, which was infiltrated with macrophages surrounded by astroglia showing palisading pattern. Ferrugination was marked in the thalamus and severe neuronal loss with astrogliotic change in the CA1-2 area of the hippocampus. Grumose degeneration was noted in the dentate nucleus of the cerebellum. This is the first report of grumose degeneration in OTC deficiency.

Pigmented squamous cell carcinoma with dendritic melanocyte colonization in the external auditory canal

A case of pigmented squamous cell carcinoma (SCC) with dendritic melanocyte colonization in the external auditory canal is reported and the previous cases are reviewed. A 65‐year‐old Japanese female was referred with a 7‐year history of otitis. The patient also had a darkly pigmented 9 × 8 mm nodule in the external auditory canal. Microscopically, the tumor was SCC, but in some areas melanin pigments were found in the cytoplasm of the tumor cells. The tumor was thus diagnosed as pigmented SCC. As well as the tumor cells, dendritic‐shaped cells colonized the tumor parenchyma and were immunohistochemically defined as melanocytes. The authors believe this is the first case of pigmented SCC with dendritic melanocyte colonization in the external auditory canal.

Olfactory bulb dysplasia: A novel subtype of neuronal migration disorder

We present a novel subtype of neuronal migration disorder found in a case of Pena‐Shokeir phenotype, in which the deformation sequence originated from neurogenic fetal akinesia. The autopsied brain showed dysplastic features of dentate and olivary nuclei as well as a bilaterally enlarged olfactory bulb with abnormal laminar structures. The laminar structures comprised four layers: (1) a superficial layer without glomeruli, (2) a neuronal cell layer containing neurons simulating mitral cells, (3) a sparse cell layer enriched with tangential neuronal fibers, and (4) a reticular layer showing a mottled appearance with the accumulation of fine reticular neurites intermingled with granule cells. To our knowledge, these malformed laminar changes have never been reported, and we propose the term olfactory bulb dysplasia.

Cerebellar basket cells of Creutzfeldt-Jakob disease: immunohistochemical and ultrastructural study.

To elucidate possible abnormalities of cerebellar basket cells of Creutzfeldt–Jakob disease (CJD), seven sporadic cases were examined neuropathologically. Recently, parvalbumin‐positive, GABAergic cerebral interneurons have been demonstrated to show early, selective loss in CJD, and the phenomenon is postulated as a cause of characteristic neurological symptoms of CJD. In this study, however, we demonstrated that the basket cells, cerebellar counterparts, were resistant even in patients with severe brain atrophy, and their processes showed intense argyrophilia and immunopositivity to phosphorylated neurofilament. They can newly be listed as CJD‐resistant neurons similar to those of the hippocampus and brainstem nuclei. The mechanism to escape cell loss is of great interest, and there might be unknown factors modulating susceptibility within parvalbumin‐positive neuronal subgroups. Furthermore, one case showed abnormal positivity with hematoxylin, crystal violet and pyronin in the basket cells. The pyronin positivity was reduced after ribonuclease digestion, suggesting that the causative substance was composed of RNA. Ultrastructurally, the fibers contained free ribosomes and amorphous electron‐dense deposits. To our knowledge, such a finding has also not been previously reported.

Meshy meningioma: a potential novel variant.

A potential novel variant of meningioma is reported. The tumor was solid, hard, white‐colored, well circumscribed in a fibrous capsule and fixed to the dura, showing no invasion into the brain parenchyma. Histopathological study presented a sparsely cellular tumor composed of cells with fine reticular or mesh‐like cytoplasm, each containing an oval nucleus. Mitotic figures were rarely seen. Immunohistochemical studies of tumor cells showed positive immunoreactivity for vimentin and epithelial membrane antigen but were negative for GFAP, desmin, neurofilament, keratin, S‐100, CD34 and CEA. Bipolar neoplastic cells and long processes were noted on ultrastructural observation; these were attached side by side to each other by desmosomes, resulting in a mesh‐like configuration. Perinuclear cytoplasm and processes were rich in intermediate filaments and rough endoplasmic reticulum. These microscopic and ultrastructural features have never before been reported among the variants of meningioma. The name ‘meshy meningioma’ is proposed for this novel variant.