Isolated infratentorial demyelinating lesion

Abstract

A 46-year-old man presented with subacute right-sided hemifacial sensory loss since 1 week. Brain MRI showed an isolated hyperintense lesion and a hypointense rim on T2-weighted imaging in the right-sided middle cerebellar peduncle associated with restricted diffusion in a concentric closed ring pattern, without gadolinium enhancement (Fig. 1). Spinal MRI was normal. C-reactive protein, antinuclear antibody, angiotensin-converting enzyme, paraneoplastic autoantibody evaluation, Lyme/HIV/syphilis serology were all normal. CSF analysis was normal apart from the presence of oligoclonal bands. Thoraco-abdominal-pelvic CT, whole-body FDG-PET, salivary gland biopsy, eye fundus, slit lamp examination, visual-evoked potentials, and optical coherence tomography scanner were all normal. While symptoms persisted, MRI 2 weeks later showed an increase in lesion size with a pattern of alternating bands of signal intensity (Balo-like) on T2-weighted imaging, partial gadolinium enhancement, and signal reversal (now hyperintense) on ADC map in the gadolinium-enhancing part of the lesion (Fig. 1). A stereotactic biopsy showed a demyelinating lesion (loss of myelin, foamy macrophages, perivascular inflammation, reactive astrocytes) in the absence of a tumoral process. Biopsy led to transient worsening of the hemifacial sensory loss. A diagnosis of an isolated infratentorial biopsy-proven demyelinating lesion was made. Intravenous methylprednisolone 500 mg od for 5 days led to improvement of the sensory symptoms. Nine months later, MRI still showed the (now only slightly) hyperintense T2-weighted lesion, in the absence of gadolinium enhancement or diffusion restriction (Fig. 1). No other lesions were seen. After 1 year of clinical and radiological follow-up, only very slight right-sided hemifacial paresthesias persisted (probably a sequella of the inflammatory lesion and/or the stereotactic biopsy performed). Restricted diffusion, T2-weighted hypointense rim, and Balo-like lesions seen in our patient correspond to what can be seen in patients with atypical idiopathic inflammatory or biopsy-proven demyelinating brain lesions [1, 2]. In a series of 69 patients with atypical idiopathic inflammatory demyelinating brain lesions (including megacystic, Balolike, infiltrative, ring-like, and unclassified type), only one had an infratentorial lesion (of the unclassified category) [2]. Recently, a series of 7 patients with a solitary demyelinating lesion in the brainstem (n = 2), the cervicomedullary junction (n = 3) or the upper cervical spinal cord (n = 2), called solitary sclerosis, has been described [3]. Evolution (follow-up of 6-year period) in these patients, in contrast to our patient (follow-up of only 1 year), was progressive leading to disability essentially due to motor impairment. In the reported 7 patients, none except one (with a post-mortem examination demonstrating an isolated pontine demyelinating lesion) had histological confirmation of demyelination. The presence of CSF oligoclonal bands, present in our case and in 4 of the 7 reported patients with solitary sclerosis, is concordant with a demyelinating process. Thus, overall, biopsy-proven isolated demyelinating lesions in the posterior fossa are very rare. Recognition of the radiological features of these often atypical lesions is D. Renard (&) G. Castelnovo P. Labauge Department of Neurology, CHU Nimes, Hopital Caremeau, Place du Pr Debre, 30029 Nimes Cedex 4, France e-mail: dimitrirenard@hotmail.com