173

10 Polyradiculopathy and Polyneuropathy

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),

Polyradiculopathy and Polyneuropathy

10

Mumenthaler / Mattle, Fundamentals of Neurology © 2006 Thieme All rights reserved. Usage subject to terms and conditions of license.

174 10 Polyradiculopathy and Polyneuropathy

a

b

Fig. 10.1 Bilateral peripheral facial nerve palsy in Guillain−Barré polyradiculitis: a acute phase, b after recovery. (From: Mumenthaler, M.: Didaktischer Atlas der klinischen Neurologie, 2nd edn, Springer, Heidelberg, 1986.)

HIV, Epstein−Barr virus (infectious mononucleosis), or Campylobacter jejuni. The last-named organism often produces axonal lesions and is associated with a particularly severe form of the illness. Immunological processes play an important role in pathogenesis; in particular, there is an elevated concentration of antimyelin antibodies. Finally, anti-GD1a antibodies are found in the rarer forms of the illness that involve axonal degeneration, but not in the more common, demyelinating forms (see above).

Clinical manifestations. The first sign is weakness of the lower limbs, beginning distally, occasionally some time after a preceding upper respiratory or gastrointestinal infection. There is no fever. Weakness ascends within a few hours or days, so that the patient becomes unable to walk. Distal paresthesiae and sensory disturbances are present in most patients, but are much less disturbing to the patient than the weakness.

Though the weakness ascends rapidly, its ultimate extent is variable. In very severe cases, the upper limbs, diaphragm, and accessory muscles of respiration are affected, as well as the muscles of the head and neck that are supplied by the cranial nerves. Dysphagia and bilateral facial palsy result (Fig. 10.1). Respiratory failure often develops rapidly and is a life-threatening condition requiring prompt treatment with intubation and artificial ventilation. In addition, involvement of the autonomic nervous system can cause life-threatening abnormalities of blood pressure regulation, cardiac rhythm, central respiratory drive, and, rarely, bladder function.

Diagnostic evaluation. The diagnosis is generally made from the clinical findings and confirmed by the charac-

teristic finding of albumino-cytologic dissociation in the CSF. This term refers to an elevation of the CSF protein concentration without any accompanying elevation of the cell count; the finding may not be present, however, until two or three weeks after the onset of illness. Electrophysiological studies usually reveal focal demyelination with conduction block, or, less commonly, axonal lesions.

Treatment. In severe cases, with profound weakness and rapidly progressive respiratory dysfunction, an intravenous infusion of immunoglobulins is indicated (0.4 g/kg body weight for five consecutive days). Another course can be given in four weeks, if necessary. Plasmapheresis, too, is effective and is recommended for all patients with rapidly ascending paresis and impending respiratory failure, even if the patient can still walk. Such patients should be hospitalized in an intensive care unit, so that their circulatory and respiratory function can be closely monitored and they can be intubated at once, if necessary. In milder cases, general supportive care often suffices: routine nursing, prophylaxis against venous thromboses, urinary catheterization if needed, and, later, physical therapy.

Prognosis. The prognosis is generally favorable. Intensive care may be needed in the acute phase, but, once this is past, the weakness usually resolves in all affected muscles (those that became weak first recover last). Recovery may take several months, however, or even up to two years in very severe cases. Most of the deaths caused by Guillain−Barré syndrome are complications of prolonged immobility (pneumonia, pulmonary embolism) or of autonomic dysfunction (respiratory failure, sudden cardiac death).

Mumenthaler / Mattle, Fundamentals of Neurology © 2006 Thieme All rights reserved. Usage subject to terms and conditions of license.

Polyradiculitis

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.

175

Polyradiculopathy and Polyneuropathy

10

Mumenthaler / Mattle, Fundamentals of Neurology © 2006 Thieme All rights reserved. Usage subject to terms and conditions of license.