2). a specific neurological syndrome. We report here the case of a patient who developed cerebellar ataxia along with auto-antibodies restricted to the GAD67 isoform. 2. Case report In November 2015, a 59-year-old woman presented with sudden onset of dizziness, vomiting and vertigo for 15 days. She denied sensory deficits and other focal neurologic or systemic symptoms, but complained of blurred vision. Neurological examination was amazing for vertical nystagmus, horizontal diplopia, and moderate right-arm dysmetria on finger-to-nose testing. Routine laboratory evaluation, brain MRI and MR-angiography were normal (Fig. 1). She was first treated for vertigo with betahistine and sulpiride, but during the ensuing 9 weeks she had a rapidly progressive neurological deterioration evolving to a pancerebellar syndrome. At examination, she had nystagmus on upward gaze, scanning speech, asymmetric dysmetria involving the 4 limbs, intention tremor, hypotonia, brisk deep tendon reflexes, right ankle clonus, and wide-based ataxic gait requiring bilateral assistance to walk. Cognition was normal. There were no other cranial nerve deficits, and she had normal strength. The score in ICARS scale was 61/100 (Trouillas et al., 1997). Open in a separate windows Fig. 1 Brain MRI. At diagnosis axial T2 (A) and axial T1-gadolinium (B) did not reveal structural abnormalities or contrast enhancement. In sagittal slices, the volume of the cerebellar vermis was stable in a control (D) at FGF2 10 months PF 3716556 from clinical onset, 6 weeks after the first neuroimaging (C). Repeat brain MRI was normal (Fig. 1). Blood tests including blood count number and renal function were normal. Specific studies for metabolic or nutritional deficits (copper, thyroid function, vitamins E and B12), autoimmune or inflammatory disorders (transglutaminase antibodies, antinuclear PF 3716556 and Ro antibodies, angiotensin-converting enzyme) and tumor markers were unremarkable. Whole-body CT scan was normal. Two CSF studies were normal except for a CSF-restricted IgG oligoclonal band. Neuronal antibody studies using frozen rat brain tissue immunohistochemistry revealed a pattern of reactivity suggestive of GAD-ab in CSF and serum (Fig. 2). Immunoblot using 2 commercial kits made up of GAD65 (Euroimmune and Ravo) were both unfavorable in serum and CSF. Serum was also unfavorable for GAD65 using a commercial RIA analysis. An in house cell-based assay using HEK293 cells transfected with recombinant human GAD65 or GAD67 (Gresa-Arribas et al., 2015) showed that both serum and CSF contained antibodies restricted to the GAD67 isoform. The titer of GAD-abs was evaluated by serial dilutions in immunohistochemistry until the specific immunoreactivity disappeared. Serum titer was 1:3600 and CSF titer 1:1200. The index of GAD-ab was calculated as previously described (Saiz et al., 2008) and it was 74.8, indicating a strong intrathecal synthesis. Open in a separate windows Fig. 2 Immunoassays for GAD-ab detection. (A, B) Immunohistochemistry on rat cerebellar tissue shows the characteristic staining of the presynaptic inhibitory terminals, especially the axon hillock of Purkinje PF 3716556 cells (*), the granular layer (GL) and dendritic tree of Purkinje cells penetrating the molecular layer (ML). At regular conditions for antibody screening this pattern was stronger in the CSF (A, dilution 1:2) compared with the serum (B, dilution 1:500), which had the immunostaining more apparent essentially in the cerebellar deep nuclei (inset, 40). (C) A commercial immunoblot was unfavorable for GAD65-ab in serum and CSF (strips 22 and 21 respectively), in contrast to the serum from another patient with PF 3716556 cerebellar ataxia and GAD-ab (strip 23). (DCE) Merged images of a cell-based assay using HEK293 cells transfected with GAD65 (D, E) or GAD67 (F, G) showing selective.