Neurosarcoidosis

A 44-year-old man with chronic anterior uveitis had his first epileptic seizure. He displayed severe psychomotor retardation, moderate apraxia of the right hand, and no other neurological symptoms. MRI and skin lesion biopsy confirmed the diagnosis. Methotrexate treatment led to marked improvement seen in a follow-up MRI after 3 months.

T2 and FLAIR imaging revealed numerous hyperintense lesions located bilaterally but asymmetrically in the subcortical and deep white matter of the cerebral hemispheres. Post-contrast images showed patchy enhancement in most of the lesions, as well as additional areas of punctate and linear enhancement, suggesting perivascular distribution.

Moderate dural thickening was noted above the left cerebral hemisphere in addition to mild sulcal effacement. Furthermore, pial-arachnoid contrast enhancement and incomplete cerebro-spinal fluid (CSF) signal attenuation on FLAIR was present along the superior and inferior frontal sulci on the left side.

SWI showed several punctate hypointensities in both thalami, indicating micro-bleeds.

Sarcoidosis is a granulomatous disease that affects multiple organ systems. Its exact cause is unknown, but it has been estimated to occur at an annual incidence of between 0.5 and 11.5 per 100,000 individuals, depending on the region. [1–3] Neurosarcoidosis is a relatively common complication of systemic sarcoidosis, affecting approximately 5-10% of patients with the disease. It can manifest in a variety of ways, often making diagnosis difficult. The demographics of affected patients are like those of systemic sarcoidosis, typically affecting individuals 30-40 years of age with a female predilection. [4–6]

Clinical presentation of neurosarcoidosis is variable, with lesions potentially involving the leptomeninges, pituitary, and parenchyma of all parts of the intracranial compartment. This can result in a range of nonspecific signs and symptoms, including raised intracranial pressure due to hydrocephalus, cranial nerve palsies, and optic nerve involvement. Neurosarcoidosis can also present with endocrine features such as diabetes insipidus, SIADH, and hypothyroidism. [7, 8] It is rare to have isolated neurosarcoidosis without systemic disease, but CNS symptoms may be the first manifestation.

Radiographic features of neurosarcoidosis can be observed in one or more of five compartments in the brain. These include the skull vault, pachymeningeal tissue, leptomeningeal tissue, pituitary and hypothalamic regions, and cranial nerves. Computed tomography (CT) scans may be used in the initial workup, but magnetic resonance imaging (MRI) with contrast is the preferred modality. [6, 9] On MRI, pachymeningeal involvement often appears as dural thickening with homogeneous enhancement, while leptomeningeal involvement may show focal or generalized enhancement, often around the base of the brain and the circle of Willis. [10] Pituitary and hypothalamic involvement may be seen as part of more widespread leptomeningeal disease, or in isolation. Cranial nerves, particularly the facial nerve and optic nerve, may also be affected. Parenchymal involvement is the most common finding and can manifest in many forms, including perivascular extension and periventricular T2 hyperintense white matter lesions. [7, 9]

The final diagnosis of neurosarcoidosis is made by considering the patient's history, symptoms, and imaging findings, as well as excluding other potential causes. If there is still uncertainty, a biopsy of the meninges, brain, or spinal cord may be necessary. A biopsy of affected extraneural tissue is however preferable. [7, 11] The clinical course and response to treatment can also help confirm or rule out the diagnosis.

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