Fundamentals . . . 173

Polyradiculitis . . . 173

Polyneuropathy . . . 176

Fundamentals

In this chapter, we will describe the characteristic syndromes produced by lesions affecting multiple nerve roots or peripheral nerves simultaneously (polyradiculopathy and polyneuropathy, respectively). If nerve roots and peripheral nerves are affected, the disorder is termed polyradiculoneuropathy. These very heterogeneous syndromes can be classified in various ways. Today, they are most commonly classified according to the following criteria:

Temporal course: polyradiculoneuropathy may present acutely with complete or partial remission, or it may take a chronically recurrent or chronically progressive course.

Etiology: polyradiculoneuropathy may be of metabolic, endocrine, toxic, genetic/hereditary, infectious, inflammatory, autoimmune, or paraneoplastic origin.

Pathology: the functioning of the nerve roots and/or peripheral nerves may be impaired either by demyelination or by axonal degeneration. Slowing of nerve conduction early in the course of the illness is a distinguishing feature of demyelinating polyradiculoneuropathy.

The general manifestations of polyradiculopathic and polyneuropathic disorders include:

paresis,

diminution or absence of reflexes,

muscle atrophy,

sensory deficits and positive sensory phenomena (paresthesia, dysesthesia),

pain (in some patients),

predominantly distal symptoms and signs in a symmetrical distribution, or, in other patients, asymmetrical severity,

usually beginning in the lower limbs,

with more or less rapid progression,

with variable involvement of the autonomic nervous system.

The extent, severity, and distribution of these manifestations vary from patient to patient. In addition, predominantly radiculopathic processes are clinically distinguishable from exclusively neuropathic processes. These two types of illness are, therefore, presented separately in the following sections.

Polyradiculitis

This term refers to an inflammatory process affecting many spinal nerve roots (most commonly the anterior ones), usually with simultaneous involvement of the proximal segments of the peripheral nerves. Inflammation of the nerve roots or nerves is usually not caused by infection, but rather by im- mune-mediated processes, e. g., an autoallergic radiculitis or neuritis following a prior, possibly asymptomatic viral or bacterial infection. Clinical variants of polyradiculitis are distinguished from one another by the degree of acuity and predominant localization of symptoms and signs. The acute form, Guillain−Barré syndrome, is the most common; the chronic form (CIDP = chronic inflammatory demyelinating polyradiculoneuropathy) is rarer, as is localized polyradiculoneuritis, which exclusively affect either the cranial nerves or the nerves of the cauda equina. Demyelinating processes are the main pathophysiological mechanism of polyradiculitis. Axonal degeneration is also present, to a varying degree, in CIDP, which explains its protracted course.

Classic Polyradiculitis (Landry−Guillain−

Barré−Strohl Syndrome)

Acute polyradiculitis is characterized by rapidly ascending paresis, accompanied by at most mild sensory disturbances. In severe cases, the cranial nerves and autonomic system can be involved. Weakness usually improves spontaneously in all involved muscles (those that became weak first recover last). The prognosis is favorable.

Epidemiology. This illness, usually called Guillain− Barré syndrome for short, can appear at any age. Its annual incidence is between 0.5 and 2 cases per 100 000 persons. It tends to appear in the spring or fall.

Etiology and pathogenesis. This syndrome probably has more than one cause. Often, no precipitating factor can be identified. In some patients, the illness is preceded by Mycoplasma pneumonia or by infection with varicella-zoster virus, paramyxoviruses (mumps),

Chronic Inflammatory Demyelinating

(Recurrent) Polyneuropathy (CIDP)

CIDP, a chronic form of polyradiculitis, has a similar pathophysiological mechanism to Guillain−Barré syndrome, the corresponding acute form. The weakness and autonomic dysfunction are usually less severe, but they last longer. The clinical manifestations fluctuate in severity, often taking a relapsing and remitting or chronically progressive course.

Pathogenesis. The idiopathic form of this condition is presumed to have an immunological basis. Immunoglobulins are found in the CSF and immunoglobulin deposits are seen in biopsy specimens of the sural nerve. There are also forms of CIDP associated with HIV or systemic lupus erythematosus.

Clinical manifestations. CIDP differs from classic, benign Guillain−Barré polyradiculitis in the following ways:

chronic or relapsing-remitting course (more than four weeks),

possibly subacute course,

pain is common,

asymmetrical distribution of neurological deficits,

recurrent cranial nerve involvement,

marked elevation of CSF protein concentration, often combined with an elevated IgG index and pleocytosis,

central nervous manifestations are more common than in Guillain−Barré syndrome,

electroneurography reveals evidence of focal demyelination or axonal damage.

Diagnostic evaluation. Electrophysiological studies reveal slowing of nerve conduction, partial conduction blocks, and a delayed F wave.

Treatment. CIDP is treated with corticosteroids or immunosuppressive agents (cyclophosphamide) for a long period. Immunoglobulins and plasmapheresis are also used, sometimes in combination with immune suppression.

!Although corticosteroids are indicated in the treatment of CIDP, they are only of questionable benefit in Guillain−Barré syndrome.

Prognosis. The prognosis is unfavorable: 10 % of patients die of the disease, 25 % remain severely disabled, and 5 to 10 % have recurrences.

Multifocal Motor Neuropathy (MMN)

This is a special form of CIDP (see above).

Clinical manifestations. MMN is characterized by asymmetrical, slowly or rapidly progressive weakness with muscle atrophy and, sometimes, fasciculations (which may make MMN difficult to distinguish from ALS). There may also be dysarthria and sensory deficits. Some reflexes are lost.

Diagnostic evaluation. Electrophysiological studies reveal sporadic, circumscribed conduction blocks, and laboratory testing often reveals elevated anti-GM1 titers.

Treatment. MMN is treated like other forms of CIDP.

Cranial Polyradiculitis

Polyradiculitis of the cranial nerves may be a component of ascending polyradiculitis, in which case it generally arises only after the limbs have become paretic. Sometimes, however, it is the first, predominant, or only clinical manifestation of polyradiculitis. The differential diagnosis of such patients must always include borreliosis and chronic meningitis (p. 112).

Miller Fisher Syndrome

Clinical manifestations. This special form of cranial polyradiculitis, which mainly affects younger male patients, is characterized by

ophthalmoplegia,

ataxia,

areflexia,

(sometimes) pupillary involvement (e. g., Adie pupil),

(sometimes) facial nerve palsy,

elevated CSF protein concentration,

(sometimes) accompanying brainstem signs.

Treatment. Miller Fisher syndrome has a favorable prognosis and generally needs no specific treatment.

Polyradiculitis of the Cauda Equina

This rare type of polyradiculitis, also called Elsberg syndrome, is characterized by isolated involvement of the sacral roots, producing distal weakness and areflexia of the lower limbs and sphincter dysfunction. Many patients are presumably due to borreliosis or a herpes virus infection.