Page 231 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

206 Loic Guillevin

knees, ankles, elbows and wrists, rather in the shoulders or hips; arthritis is typically absent
and joint deformities do not occur.

Nervous System Involvement

Peripheral Neuropathy
Peripheral neuropathy is the commonest peripheral nervous system (PNS) manifestation,

so noted in up to 75% of affected patients [35, 36], and may be the earliest symptom in up to
a third. Segmental edema precedes the development of cranial nerve palsy reflecting
capillary-permeability dysfunction. Hypo- and hyperesthesia, dysesthesia and frank pain,
resulting from sensory nerve involvement, are prominent and earliest presenting complaints.
Motor deficits typically affect the legs often preceding sensory involvement, commencing
suddenly with involvement of one nerve at a time, termed mononeuritis or mononeuropathy
multiplex, in one-half to two-thirds of patients [36, 37]. The peripheral neuropathy is typically
distal and asymmetric, preferentially affecting the fibular, sural, radial, ulnar, and median
nerves. A symmetrical process may be observed due to the coalescence of nerve lesions.
Cerebrospinal fluid (CSF) findings are typically normal and electromyography (EMG) and
nerve conduction studies (NCS) are compatible with an axonopathy process evidenced by
reduced compound muscle action potential (CMAP) amplitudes with normal or near normal
conduction velocities. Rare patients are encountered with brachial plexus neuropathy [38] and
peripheral motor conduction block [39] indicative of a demyelinating process similar to
Guillain–Barré syndrome or other acquired demyelinating neuropathies, and peripheral nerve
entrapment [40]. Sensory neuropathy may be the consequence of isolated small fiber
involvement that is not a consequence of vasculitis [41]. Mononeuropathy multiplex regresses
slowly and improves to a variable degree in over 12 to 18 months following effective therapy
without residual lesions, however paresthesia can persist longer or indefinitely.

Isolated peripheral nerve vasculitis, categorized as a single organ vasculitis (SOV) (42)
by the 2012 Revised CHCC Nomenclature [5], differs from the isolated phenotypic
expression of PAN that often conveys a more benign and chronic outcome.

Central Nervous System Manifestations

Central nervous system (CNS) involvement was observed in 4.6% of patients with PAN
[36]. Affected patients with encephalopathy have altered cognitive function with
disorientation, psychosis, hallucinations. There can be focal or multifocal neurological
disturbances leading to seizures, strokes or subarachnoid hemorrhages [43] resulting from
focal cerebral arteritis leading to cerebral artery-aneurysm rupture and hematoma,
alternatively due to malignant hypertension. Distal occlusion of spinal vessels engenders
sphincter dysfunction [44]. MRI of the brain typically shows non-specific T2-weighted white
matter subcortical hyperintensities, while MR angiography (MRA) and conventional cerebral
angiography may be normal.

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