Sarcoidosis is a great masquerader of other systemic diseases (particularly tuberculosis) and in a large number of patients with neurosarcoidosis presents with nonneurologic issues. Neurologists should always be aware of certain clues such as pulmonary involvement, eye disease (especially uveitis), dermatologic manifestations such as erythema nodosum, lymphadenopathy, joint pain, and other systemic symptoms (such as unexplained fever), which can eventually guide them to a correct diagnosis.
As a complicated multisystemic disease, sarcoidosis affects various parts of human nervous system and such widespread process leads to a wide range of
Fig. 5.3 x10: Medium-power photomicrograph showing a parenchymal granuloma with central epithelioid cells and surrounding lymphocytic infiltrate (H&E, original magnification x 100)
neurological manifestations. Cranial nerve palsy and neuropathy, either due to granuloma, elevated intracranial pressure, or granulomatous basal meningitis, is the most common neurological presentation of neurosarcoidosis. Among the cranial nerves, the facial and the optic nerves are the most commonly affected. Bilateral facial nerve palsy due to neurosarcoidosis may occur, or the seventh cranial nerve may be affected sequentially.
While patients with neurosarcoidosis may present with rapidly progressing papilledema, other cranial nerves including olfactory, optic, oculomotor, vestibulocochlear, and uncommonly trigeminal, may be affected either alone or in combination. The pathologic process of the sarcoidosis can affect the cranial nerve nucleus or at any point within their anatomic pathway. Patients with Heerfordt’s syndrome present with cranial neuropathy (most commonly facial nerve palsy), uveitis, fever, and enlargement of parotid gland. Such a unique combination is highly suggestive of neurosarcoidosis. Also, Horner’s syndrome which develops from the disruption of cervical sympathetic fibers could be a manifestation of neurosarcoidosis. Pupillary abnormalities including Argyll-Robertson pupil and Adie’s pupil have also been described in sarcoidosis.
Leptomeningeal involvement due to widespread meningeal infiltration of brain occurs in the presence or absence of parenchymal brain lesions and clinically may be symptomatic or may manifest as subacute or chronic aseptic meningitis, basilar polycranial neuropathy, and neuroendocrine abnormalities. Clinicians who manage these patients should bear in mind that headache and seizures may stem from meningitis, hydrocephalus, space-occupying lesions, or opportunistic infections (particularly in immunocompromised patients). Headache in these patients less often originates from trigeminal neuropathy or worsening of coexisting migraines . In patients with neurosarcoidosis, seizures may be the initial presentation of the underlying disease process, and they may experience any type of seizures. Manifestation of the seizure in these patients may designate chronicity and an unfavorable prognosis .
Rarely, neurosarcoidosis may result in stroke due to penetration of the endothelial layers of small or large blood vessels, with disruption of the media and internal elastic lamina, resulting in obstruction of the vessel and ischemic cerebral infarct . Other possible stroke pathology suggested includes sarcoidosis-associated mass lesion compression of an intracranial artery, necrotizing arteritis with fibrinoid necrosis of the media and massive leukocyte invasion , and cardiac granulomatous inflammation resulting in cardiogenic emboli. Cerebral and dural venous sinus thrombosis is also a potential, however, rare complication of this inflammatory process [5, 10].
With more diffuse leptomeningeal disease, headache may be accompanied by gait dysfunction, cognitive changes, and/or seizures, suggesting involvement of the brain parenchyma. Patients presenting acutely with this complex of symptoms should be evaluated urgently for hydrocephalus, which can often complicate severe cases of leptomeningeal inflammation and is considered a neurologic emergency. Hydrocephalus is another interesting clinical feature of neurosarcoidosis, which may be due to meningeal infiltration of the arachnoid granulations or cerebral aqueduct. Patients with neurosarcoidosis may develop cauda equina syndrome due to meningeal infiltration of the lumbosacral nerve roots.
Myelopathy in the context of neurosarcoidosis occurs as a result of spinal lep- tomeningeal infiltration, extensive myelitis, or both. Cases of neurosarcoidosis with longitudinally extensive myelitis which span an average of 3.9 segments (a significant differentiating feature from multiple sclerosis with smaller and patch cord lesions) have been reported. The most significant differential diagnoses of neurosarcoidosis patients with such extensive myelitis include multiple sclerosis, neuromyelitis optica, lupus myelitis, Sjogren’s syndrome, and infectious diseases.
Neuroendocrine abnormalities of neurosarcoidosis, which stem from hypothalamic and pituitary involvement by the subependymal granulomatous invasion of the third ventricle region, includes hypothalamic hypothyroidism, hypogonadotro- pism, SIADH, diabetes insipidus, growth hormone deficiency, and hyperprolactinemia .
Neurosarcoidosis may be associated with various nonspecific neuropsychiatric symptoms such as memory loss, fatigue, mood disturbances, and other behavioral issues, without evidence of a CNS lesion. These are attributed primarily to underlying systemic disease, medication side effects, depression, and sleep disorders such as sleep apnea syndrome and primary hypersomnia.
Peripheral nervous system involvement in the process of neurosarcoidosis includes asymmetric polyradiculoneuropathy, mononeuritis multiplex, small fiber sensory neuropathy with autonomic dysfunction, AIDP, CIDP, and subacute length- dependent axonal polyneuropathy. Mononeuropathy is another manifestation of neurosarcoidosis and the ulnar and peroneal nerves are the most frequently affected. Autonomic dysfunction symptoms include orthostatic hypotension, gastrointestinal dysmotility, and disorders of sweating. Small fiber neuropathy of neurosarcoidosis can involve autonomic nerve fibers and cause cardiac sympathetic denervation with cardiac arrhythmias and may cause restless leg syndrome . Patients with neurosarcoidosis may develop myopathy with granulomatous muscle involvement, and this may be clinically symptomatic or remain asymptomatic. In symptomatic cases, patients complain of myalgia, weakness, and muscle tenderness and suffer from cramps and muscle atrophy. Acute myositis in the context of neurosarcoidosis is uncommon and the myopathy more often takes a chronic course.