The diagnosis of neurosarcoidosis is very challenging especially in the absence of other symptoms. Computed tomography (CT) and magnetic resonance imaging (MRI) of the brain are essential in the assessment of central nervous system (CNS) involvement, with MRI now the modality of choice due to the superiority of the images. Ring-enhancing lesions have not been reported in neurosarcoidosis, so our biopsy-proven case represents the first such presentation. Lymph nodes and other organs involved in sarcoidosis typically exhibit intense uptake of Fluorine-18-labelled 2-deoxy-2-fluoro-D-glucose (FDG) on positron emission tomographic (PET) imaging. Thus, whole body FDG PET has been used to assess the extent of pulmonary and extra-pulmonary sarcoidosis. To date, no report on FDG PET in neurosarcoidosis has been published. Our report, then, is also the first report of FDG-PET imaging in biopsy-proven intracranial sarcoidosis.
A 22-year-old man presented with 9 months of progressive memory disturbances, unsteady gait, vomiting, and urinary incontinence. He had no other symptoms. He was somnolent but arousable to verbal stimuli, oriented to person and situation but not to time or location, and had short and long-term memory loss. Cerebellar signs included a stumbling shuffling gait, inability to walk a straight line, inability to perform heel-shin testing, and abnormal rapid alternating movements. The remainder of his physical examination was normal. Biochemical, haematological, microbiological and immunological testing remained unrevealing. Cerebrospinal fluid (CSF) was clear, with normal glucose and total protein, total leukocytes 11 cells/mm3 (90% lymphocytes), and negative smears for cryptococcus and acid fast bacilli. CSF cultures were negative.Chest radiograph showed enlarged hilar shadows; chest CT confirmed mediastinal lymphadenopathy without interstitial disease. MRI of the brain showed multifocal disease with ependymal enhancement, skull base meningeal inflammation, a ring-enhancing lesion in the left caudate nucleus (Figure 1) and obstructing hydrocephalus.Brain and whole body PET scans were obtained, searching for an underlying neoplasm. PET images of the brain showed intense FDG uptake in the brain lesions, correlating with the MRI findings (Figure 2). Body images showed extensive FDG uptake in multiple node chains; the intrathoracic nodal involvement had a “Christmas tree” configuration, typical for sarcoidosis.A stereotactic biopsy of the ring enhancing lesion yielded non-caseating granulomas. No malignant cells, acid-fast bacilli, bacteria, Toxoplasma, or fungal organisms were found. All cultures of the biopsy remained negative.The patient started on prednisone, 60 mg daily; a ventriculoperitoneal shunt was implanted for residual hydrocephalus. He rapidly regained full alertness and orientation, full urinary continence and could again walk properly with minimal gait disturbance. On a follow-up visit 6 months later, he exhibited continuing improvement.DISCUSSION: Neurosarcoidosis remains a diagnostic challenge. Radiologic imaging studies, particularly the MRI, are essential in the evaluation of suspect patients; however, the MRI findings are not specific for sarcoidosis. Reported manifestations of neurosarcoidosis on MRI include nonenhancing periventricular white matter lesions; meningeal enhancement; hydrocephalus; cranial nerve involvement; enhancing brain parenchymal lesions; dural mass lesions; and spinal cord involvement. Thus far, ring-enhancing lesions have not been reported. Such a finding usually raises a differential diagnosis list of infectious processes, primary neoplasms, metastases, demyelinating diseases, and contusions.Our patient had involvement of lymph nodes on CT and PET scanning quite typical of sarcoidosis, assisting in the diagnosis but not excluding a separate etiology for the CNS involvement. The diffuse involvement of the brain demonstrated on MRI was also typical for sarcoidosis, but the ring-enhancing lesion was quite unusual. Stereotactic biopsy with negative stains and cultures of that lesion provided strong evidence that this lesion represented the granuloma of sarcoidosis.
We claim, then, the first report of the ring-enhancing lesion and FDG PET in neurosarcoidosis.
M. Raees, None.