Teaching Case

A 42-year-old man presented to ER with hallucinations and delirium. Initial work up revealed both intracranial and pulmonary lesions thought to be neurosarcoidosis, for which he was put on high dose steroids. A hilar node biopsy was obtained but results were inconclusive. Neurosurgery performed a stereotactic brain biopsy for definitive diagnosis.

Brain MRI shows a remarkable accentuation of parenchymal vessels throughout the full thickness of the cortex and white matter in cerebral hemispheres, basal ganglia, brainstem and cerebellum. FLAIR images (Fig. 1) demonstrate minimal periventricular subependymal margin FLAIR signal abnormality outlining both lateral ventricles, suggesting accentuation of the periventricular subependymal vascular zone, especially in the vicinity of the frontal horns and the splenium of the corpus callosum.
Gadolinium-enhanced images (Fig. 2, 3) demonstrate diffuse engorgement of multiple vascular structures extending from hemispheric cortex through subcortical white matter, deep white matter and subependymal margins on both cerebral hemispheres as well as throughout cerebellum and brainstem, of concern for a vasculitis type process.
Susceptibility-weighted images (Fig. 4) also demonstrate a remarkable accentuation of parenchymal vessels.
DSA ruled out dural fistula (Fig. 5).

We report a case of meningothelial hyperplasia (MH) in the cortex and underlying white matter in a 42-year-old male patient who presented with hallucinations, with imaging findings initially thought to be a central nervous system vasculitis such as primary angiitis of the central nervous system, diffuse proliferative cerebral angiopathy or CADASIL. Neurosarcoidosis was excluded by hilar node biopsy.
The cells forming the pia/ arachnoid trabeculae and septae of the subarachnoid space are called leptomeningeal cap cells, also known as meningothelial cells (MECs). These cells covering the neural tissue are connected via tight junctions, gap junctions, and desmosomes and are active immunologically in phagocytosis mechanism and production of inflammatory cytokines such as IL-6 and IL8. [1, 2]
The MECs cells proliferate in response to several stimuli such as trauma, haemorrhage, age-related, chronic renal failure, hypertension and adjacent to optic nerve pilocytic astrocytomas.
MH is a new entity that could cause diagnostic difficulties with meningioma. According to Perry et al. the packing of more than 10 layers of MECs identifies meningothelial hyperplasia, showing frequent PR immunoreactivity and occasional polyploid cells [3]. Different from classic meningiomas, genetic mapping show no evidence for NF2 or 4.1 B gene deletions on chromosome 18, or Merlin or protein 4.1B losses of expression by immunohistochemistry [3, 4].
MRI demonstrates a remarkable accentuation of parenchymal vessels throughout the full thickness of the cortex and white matter in both cerebral hemispheres, basal ganglia, brainstem and cerebellum and minimal periventricular subependymal margin signal abnormality outlining both lateral ventricles. Gadolinium-enhanced images demonstrate diffuse engorgement of multiple vascular structures extending from hemispheric cortex through subcortical white matter, deep white matter and subependymal margins on both cerebral hemispheres as well as throughout cerebellum and brainstem.
As part of the extensive work up of this patient, vasculitis and dural fistula were indeed ruled out by DSA.
The cortical biopsy final pathologic report was meningothelial hyperplasia within subarachnoid space of a segment of the cortex and underlying white matter, with scattered inflammatory cells. No granulomas, vasculitis or infectious aetiology were identified.