Morikazu Ueda

Comparison of metastatic brain tumour models using three different methods: the morphological role of the pia mater

As methods of cancer diagnosis and treatment progress, interest in metastatic brain tumours continues to increase. There are many studies using various methods of animal model and we considered that each model reflects different pathological processes because of the unique composition of the brain. We prepared metastatic brain tumour models using three different methods. In this study, we attempted to elucidate the roles of the pia mater in brain metastasis. The metastatic foci showed an angiocentric pattern, forming collars of neoplastic cells, and were designated ‘perivascular proliferations’. Furthermore, we observed neoplastic cells that infiltrated the brain parenchyma, the border of which had become indistinct. These were labelled ‘invasive proliferations’. The internal carotid artery injection model reflects haematogenous metastasis. In this model, both perivascular and invasive proliferations were observed. The intrathecal injection model reflects leptomeningeal carcinomatosis. In this model, metastasis to the meninges was observed. In the stereotactic injection model, the tumour proliferation at the injection site and the infiltration into the brain parenchyma were observed. The pia‐glial membrane serves as a scaffold when neoplastic cells spread to the perivascular space forming angiocentric pattern. The pia‐glial membrane is found between the brain parenchyma and blood vessels. Blood vessels penetrate the brain through tunnels known as perivascular spaces that are covered by pia mater. Three different methods which we prepared reflect three different pathological processes. Our findings suggest that the pia mater is a critical factor in brain metastasis.

Localisation of sensory motor cortex during surgery by changes of cortical surface temperature after median nerve stimulation

Echoencephalography revealed residual tumour below the cortical surface. However, it was not possible precisely to identify whether the residual tumour was situated in the sensory or motor cortex. Moreover, it was also impossible to determine the border of the cortex because of difficulty in placing the multiple electrode arrays on the swollen and slightly injured cortical surface. Thermomapping was carried out by thermovision with digital image processing (TVS 100ME, Nippon Avionics, Japan) during stimulation by 0·5 ms constant-current pulses delivered to the median nerve at the wrist at an intensity capable of producing a moderate thumb twitch. The stimulus rate was 2/s. The thermovision camera included a 100 ms scanning time, with each scan consisting of the average of 16 measurements with a thermosensitivity of 0·01oC and a digitised thermoimage of 120 160 pixels. The rectal temperature of the patient was controlled at 36·5oC under general anaesthesia with isoflurane. The thermovision camera was focused on the cortical surface with a zoom lens. The figure shows typical changes in cortical temperature after contralateral median nerve stimulation. It was clearly shown that changes in cortical temperature corresponded strictly to contralateral median nerve stimulation. Namely, the temperature increased during stimulation and decreased immediately after interruption of stimulation. By thermovision monitoring, the area where changes in temperature were observed corresponding to median nerve stimulation was proved to be the site of metabolic response in the sensory cortex. As a result, the entire residual tumour under the identified sensory cortex could be removed without danger of postoperative motor paresis. The thermal response to median nerve stimulation is considered to be a neurovascular response. The molecular organisation of the radial blood vessels which are normally oriented to the cortical surface and have a regular distribution over it may result in highly efficient localisation of cortical heat transport by cerebral blood flow. The increase in cortical temperature results from initial metabolic activity and heating the sensory cortex following neuronal activities after stimulation of thalamic cortical tracts. From this mechanism, changes in cortical temperature can reflect cortical activities following noxious stimuli. We have shown that the sensory cortex can be identified by means of thermoimaging during neurosurgery.

Solitary metastasis of renal cell carcinoma to the third ventricular choroid plexus with rapid clinical manifestation by intratumoral hemorrhage

A 72-year-old man who had undergone nephrectomy for left renal cell carcinoma (RCC) presented with worsening of cognitive function and frequent loss of consciousness. Computed tomography (CT) revealed tumor mass in the third ventricle and hydrocephalus. A ventriculoperitoneal (VP) shunt was placed to treat the hydrocephalus. The postoperative course was uneventful, and he was followed closely without aggressive therapy. Four months after surgery, the tumor expanded rapidly due to intratumoral hemorrhage and he died due to sepsis. The autopsy findings revealed a solitary metastatic RCC in the third ventricle, with massive intratumoral hemorrhage. Solitary metastasis of RCC to the third ventricle is quite rare and difficult to treat. The case report highlights that early diagnosis and treatment are critical, even in slowly progressive RCC patients, because of the possibility of intratumoral hemorrhage.

Automated voxel-based analysis of brain perfusion SPECT for vasospasm after subarachnoid haemorrhage

Background We evaluated regional cerebral blood flow (rCBF) during vasospasm after subarachnoid haemorrhage (SAH) using automated voxel-based analysis of brain perfusion single-photon emission computed tomography (SPECT).