INTRODUCTION

Neurologic complications occur in approximately 5 percent of patients with sarcoidosis [1-4]. Neurosarcoidosis is a diagnostic consideration in patients with known sarcoidosis who develop neurologic complaints and in patients presenting de novo with a constellation of findings consistent with the disease [5,6]. Approximately 50 percent of patients with neurosarcoidosis present with neurologic difficulties at the time sarcoidosis is first diagnosed. One-third of those with neurosarcoidosis have or develop more than one neurologic manifestation of their disease.

The diagnosis and management of neurosarcoidosis will be reviewed here. General issues related to sarcoidosis and its pathogenesis are discussed separately. (See "Clinical manifestations and diagnosis of sarcoidosis" and "Pathogenesis of sarcoidosis".)

CLINICAL FEATURES

Any portion of the central or peripheral nervous system can be affected by sarcoidosis. Common syndromes include:

• Cranial mononeuropathy. Peripheral facial nerve palsy develops in 25 to 50 percent of patients with neurosarcoidosis [2,6,7]. The facial nerve palsy can be unilateral or bilateral (simultaneous or sequential) and recurrent. Optic neuropathy and cranial nerve VIII dysfunction can lead to intermittent or progressive visual, auditory, or vestibular dysfunction. (See "Optic neuropathies", section on 'Sarcoidosis'.)
• Neuroendocrine dysfunction typically occurs with hypothalamic inflammation, resulting in polyuria or disturbances in thirst, sleep, appetite, temperature, or libido. Hypothalamic or pituitary lesions may also cause thyroid, gonadal, or adrenal abnormalities [6,8]. (See "Causes of hypopituitarism".)
  
  One such manifestation, polyuria, can result from one or more factors in patients with sarcoidosis. Direct hypothalamic involvement can lead to central diabetes insipidus or primary polydipsia, while hypercalcemia (due to production of calcitriol by activated macrophages) can cause nephrogenic diabetes insipidus [9]. (See "Hypercalcemia in granulomatous diseases".) Thus, all patients with sarcoidosis and polyuria require a water restriction test to establish the correct diagnosis. (See "Diagnosis of polyuria and diabetes insipidus".)
• Granulomatous inflammation in a perivascular distribution can involve the brain and produce partial or generalized seizures, or a restricted or generalized encephalopathy/vasculopathy [6,7]. Patients can present with cognitive or behavioral problems and/or focal neurologic deficits referable to the anatomic area involved. In rare cases, this manifests as a focal cerebral infarction [10].
• A myelopathy or radiculopathy can occur if granulomatous inflammation affects the spinal cord [6,7,11,12]. The lesions are typically perivascular, they can be extramedullary or intramedullary, and can involve the cauda equina.
• Communicating or noncommunicating hydrocephalus may develop acutely or subacutely. Asymptomatic ventricular enlargement may be incidentally detected by imaging studies [13]. Sudden death can rarely result from acute obstruction to CSF flow.
• Meningeal involvement can take the form of either an acute aseptic meningitis or a chronic meningitis. Meningeal mass lesions also can develop.
• Peripheral neuropathic presentations include a mononeuropathy, mononeuritis multiplex, and generalized sensory, small fiber sensory, sensorimotor, autonomic and motor polyneuropathies [14]. The symptoms can be acute, subacute, or chronic; electromyography usually reveals an axonal neuropathy. In addition, an acute generalized demyelinating motor neuropathy similar to the Guillain-Barré syndrome also has been described [15]. (See "Treatment and prognosis of Guillain-Barré syndrome in adults".)
• Carpal tunnel syndrome appears to be more common among patients with sarcoidosis than the general population [16-18]. (See "Etiology of carpal tunnel syndrome".)
• Muscle involvement includes asymptomatic microscopic nodules, isolated palpable nodules, an acute or chronic proximal myopathy, and muscle atrophy [19].

Patients presenting with neurosarcoidosis may have no systemic features of the disease. In one case series, non-neurologic symptoms were present in less than one-fourth of patients and were most commonly anterior uveitis, cough and dyspnea, renal impairment, rash, and polyarthritis [6].