Fig. 2

a Patient 1: an epidermoid cyst in pre-pontine cistern. Axial T2 W image and post contrast enhancement of the lesion. Patient 2: Axial T2W and FLAIR images show focal hyperintense area in left periventricular region. Patient 4: loss of white matter and cortical atrophy on FLAIR images. b Muscle MRI images of patient 1. Images in the first row are at mid-thigh level. T2 W axial images (1, 2), T1 W images (3, 4) show atrophy with fatty replacement of bilateral biceps femoris, semimembranosus & semitendinosus. STIR images (5, 6) showing no signal change in the involved muscles. Images in the second row are at calf level. T2 W axial images (7, 8), T1 W axial images (9, 10) are showing fatty replacement of the gastrocnemius & soleus. Axial STIR images (11, 12) show no significant signal changes. c Repetitive standard 3 Hz slow nerve stimulation (5th wave decrement) in Patient 1. Quadriceps demonstrated 21.1% decrement, nasalis shows 30.3%, orbicularis oculi shows 26.5% and no significant decrement detected from the tibialis anterior muscle. d Quadriceps muscle biopsy of patient 1: HE (1–2) showed polygonal fibres with peripherally placed nuclei and minimal variation in fibre size. No evidence of vacuoles, some occasional fibres showed internalized nuclei. Masson’s Trichrome (3) showed no endomysial fibrosis. Modified Gomori (4) trichrome stain showed thin subsarcolemmal accumulation while NADH stain (5–6) showed increase in subsarcolemmal accumulation. COX-SDH stain (7–8) detected COX deficient fibres in more than 50% of fibres. Electron microscopy (9–10) showed abnormal mitochondrial structure and cristae. Scale bar: 1: 50 μm; 2,4: 20 μm; 3,5,6: 100 μm; 7-8: 1 μm.