Chapter 105 - Neuropathies with Systemic Vasculitis

The autoimmune neuropathies represent an important category of the peripheral neuropathies. We need to recognize the potential implications of autoimmune neurology—a new subspecialty in neurology that has truly launched. We review the clinical patterns, diagnostic paradigms, etiopathogenesis, and therapeutic strategies of autoimmune neuropathies such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, immunoglobulin M paraproteinemic neuropathy, nodopathies, as well as immune neuropathies associated with other systemic immune disorders. Making a diagnosis can be challenging and first assisted by electrophysiologic and sometimes pathologic sampling, with autoimmune biomarkers providing increased assistance. The importance of autoimmune neuropathies cannot be overstated as many of the disorders are treatable and reversible. In this chapter, we provide an overview of how the field developed and describe some of the ongoing challenges.

Vasculitis is characterized by blood vessel inflammation, which may lead to tissue injury. It may be idiopathic (primary vasculitis) or attributable to definable causes (secondary vasculitis). Vasculitic neuropathy is defined as a peripheral neuropathy due to necrotizing vasculitis of the vasa nervorum, leading to various clinical phenotypes, with painful multiple mononeuropathy being the most classical. Although the electrophysiological, clinical, biological, or radiological signs may be indicative, the diagnosis of vasculitic neuropathy needs to be confirmed by nerve biopsy, showing a combination of vascular and inflammatory features. The treatment is based on the guidelines of the underlying disease, but corticosteroids and immunosuppressants are the treatments of choice, except in virus-associated vasculitis.

Ultrasound of the peripheral nerves (PNUS) can be used to visualize nerve pathologies in polyneuropathies (PNP). The aim of this study was to investigate, whether PNUS provides additional information in patients with proven systemic vasculitic neuropathies (VN).

Systematic ultrasound measurements of several peripheral nerves, the vagal nerve and the 6th cervical nerve root were performed in 14 patients and 22 healthy controls. Nerve conduction studies of the corresponding nerves were undertaken. Finally, the measured results were compared to a study population of demyelinating immune-mediated and axonal neuropathies.

Patients with VN displayed significant smaller amplitudes of compound muscle action potentials (CMAP) (p < 0.05) and sensory nerve action potentials (SNAP) compared to healthy controls, while conduction velocity did not differ between groups. The mean nerve cross-sectional areas (CSA) were increased in several peripheral nerves compared to the controls, most prominent in tibial and fibular nerve (p < 0.01). PNUS revealed nerve enlargement in most of the clinically and electrophysiologically affected nerves (22 out of 31) in VN. Nerve enlargement was more often seen in vasculitic neuropathies than in other axonal neuropathies, but significantly rarer than in demyelinating neuropathies.

Focal CSA enlargement in one or more nerves in electrophysiologically axonal neuropathies can be a hint for VN and thus facilitate diagnostic and therapeutic procedures.

Organized anatomically into categories spanning from the lower motor neuron to muscle, this chapter describes the neuromuscular complications of systemic medical disease. The text focuses on diagnosis and treatment of the disorders. The neuromuscular effects of toxic exposures are also discussed. Numerous tables are included to help with the diagnostic process.

Conditions leading to vasculitis of peripheral nerves are heterogeneous. They can be primary or secondary and systemic or nonsystemic. Thus, immune pathology is most likely diverse and differs between diseases. This article focuses on processes of the cellular and humoral immune system related to vasculitis, with an emphasis on those diseases where knowledge has accumulated in recent years. These are the antineutrophil cytoplasmic autoantibody-associated vasculitides, vasculitis associated with cryoglobulinemia and hepatitis C, and nonsystemic vasculitic neuropathy.