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Neurological manifestations of Churg–Strauss syndrome

Churg–Strauss syndrome (CSS) is a rare systemic granulomatous and necrotic vasculitis of the smalland medium-sized arteries manifesting with a prodromal phase as bronchial asthma, chronic paranasal sinusitis, nasal polyps, or pulmonary infiltrations and with a vasculitic phase as multisystem disease with affected intestines (multiple ulcera causing chronic abdominal pain), heart (myocarditis, infarction), kidneys, joints (arthritis), or the nervous system and goes along with eosinophilia and elevated anti-myeloperoxidase antineutrophil cytoplasmic antibodies (ANCA) in about one-third of the cases [1,2]. The cause of CSS is unknown in the majority of the cases, but in single cases, it is induced by leukotriene-receptor antagonists. Neurological involvement occurs in 59–86% of the cases during the vasculitic phase with the peripheral nervous system (PNS) more frequently affected than the central nervous system (CNS) [2]. CSS responds favourably to steroids, cyclophosphamide, azathioprin, mycophenolate mofetil, or rituximab [3]. Central nervous system involvement is found in <10% of the patients and is usually one of several other manifestations (Table 1) [2,4,5]. Isolated CNS manifestation of CSS is rare [4]. The most frequent of the CNS manifestations is stroke [5], which may be attributed to vasculitis of the intracerebral arteries or to involvement of the heart with development of cardiomyopathy or arrhythmias and intracardiac thrombus formation. The second most frequently occurring CNS manifestation of CSS is intracerebral bleeding, which is attributed to vasculitis of the intracerebral arteries or abnormal coagulation or fibrinolysis. More rarely, CSS manifests in the CNS as subarachnoid bleeding caused by dissection of the vertebral artery, as encephalopathy with psychiatric disturbances, epilepsy, hydrocephalus, headache, sinus venous thrombosis, or as optic neuritis (Table 1) [2,4]. Cerebral computed tomography scans may show hypodensities in the thalamus [5] and cerebral magnetic resonance imaging (MRI) may show bifrontal polar gyral enhancing lesions [4]. MRI may also show T2-hypointensities with diffuse enhancement of the meninges and chorioid plexus, representing granulomatous infiltration. Occasionally, there may be eosinophilic infiltrations of medium-sized leptomeningeal arteries [4]. Cerebrospinal fluid investigations may reveal pleocytosis or elevated protein [4]. Peripheral nervous system manifestations occur in up to three quarters of the patients and include most frequently mononeuritis multiplex, followed by symmetrical polyneuropathy [2], cranial or peripheral mononeuropathy, cutaneous sensory neuropathy [3] or myositis (Table). In a single patient, the phrenic nerve was exclusively affected. The characteristic axonal loss occurs in myelinated as well as unmyelinated fibres. Cutaneous sensory neuropathy is caused by multifocal inflammation of the small sensory nerves of the skin [3]. Particularly, polyneuropathy may be associated with a positive ANCA status [1]. In this issue of the journal, Wolf et al. [6] report a prospective study in 14 patients with CSS of whom 12 presented with neurological involvement. Eight patients had mononeuritis multiplex, three axonal polyneuropathy, three neuropathy of cranial nerves and two patients had a stroke. Amongst the patients with multiplex mononeuropathy, the nerves most frequently affected were the sural, common peroneal, posterior tibial, median, ulnar, radial, deep peroneal and lateral femoral cutaneous nerves. Severe pain was the initial clinical manifestation in eight of 11 patients with PNS involvement. Therapy included steroids in all patients, and additionally cyclophosphamide in nine, azathioprin in five, mycophenolate mofetil in four, intravenous immunoglobulins in two and rituximab in one. During a follow-up of 31 months on the average, symptoms of neuropathy improved under immunosuppressive therapy despite the persistence of the axonal lesion. Neurological manifestations during follow-up were stroke, trigeminal neuropathy, vestibular neuronitis, or migraine-like headache. Overall, the relapse rate and Table 1 Clinical neurological manifestations of CSS