Expression pattern of synaptic vesicle protein 2 (SV2) isoforms in patients with temporal lobe epilepsy and hippocampal sclerosis.

AIMS: Synaptic vesicle proteins 2 (SV2) are neuronal vesicles membrane glycoproteins that appear as important targets in the treatment of partial and generalized epilepsies. Therefore, we analysed the expression of SV2 isoforms in the hippocampus of patients with temporal lobe epilepsy (TLE). METHODS: SV2A, SV2B and SV2C immunostaining and QuantiGene branched DNA assay were performed on biopsies from 31 consecutive TLE patients with mesial temporal sclerosis (MTS) and compared with 10 autopsy controls. SV2 expression was further compared with Timm's staining, and synaptophysin, Zinc transporter 3 (ZnT3), dynorphin, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter (VGAT) expression. RESULTS: In TLE patients, SV2A and SV2B expression was decreased in areas of synaptic loss. SV2C, which is weakly expressed or absent in the hippocampus of controls, was overexpressed in 10/11 cases with classical MTS1A and mossy fibre sprouting but not in cases with other types of MTS. SV2C staining was located in the inner molecular layer of the dentate gyrus and colocalized with dynorphin, ZnT3 and VGLUT1, suggesting selective expression in presynaptic glutamatergic Zn(2+) -rich terminals of abnormal sprouting fibres. SV2 expression patterns correlated with histological subtypes of MTS, but not with clinical features or therapeutic regimens in this patient cohort. CONCLUSION: In classical MTS1A, the expression of SV2 isoforms is altered with a marked decrease of SV2A and SV2B paralleling synaptic loss and a selective increase of SV2C in sprouting mossy fibres. These findings suggest a different physiology of sprouting synapses and the possibility to target them with SV2C-specific strategies.

Giant cell ependymoma of the thoracic spinal cord.

We report a new case of giant cell ependymoma (GCE) of the thoracic spinal cord. Ependymomas predominate in children and young adults and are frequently intracranial and infra-tentorial. However, a second age peak at 30-40 years is reported for spinal tumours. Microscopically, ependymomas show a large variety of histological features, among which a rare variant with giant cells. This 59-year-old woman presented with a 6-month history of numbness and burning sensation affecting the left lower limb and hemi-trunk. A cervico-thoracic MRI revealed a solid intra-medullary tumour at the level of T1-T3, slightly T1-hypointense, T2-hyperintense and contrast enhancing. A complete surgical resection was carried out through a C7 to T4 laminectomy. Recovery was complete with no sign of recurrence at 18-month follow-up. The initial histological diagnosis of glioblastoma was challenged on the basis of the imaging and operative findings of a well-circumscribed tumour. The case was sent to us for second opinion and we diagnosed a GCE, WHO grade II, with a biphasic pattern including a predominant giant cell component (>90%), with genetic evidence of polyploidy, and a very limited classic component, showing a characteristic loss of chromosome 22. Our report adds to the clinical, imaging, pathological and genetic characterisation of GCE and brings the first genetic evidence that these rare tumours are at least bi-clonal. It also suggests that GCE have a good prognosis after complete surgical resection.