Mononeuritis Multiplex: is characterized by lesions of m ultiple nerve roots, peripheral nerves or cranial nerves. I t is due either to involvement of the vasa nervorum or to malignant infiltration of the nerves.Sometimes there will be overlap between in the course of the nerves affected so in this case the disease will resemble polyneuropathy. Investigation of patients with an acute mononeuritis multiplex should be urgent since vasculitis is a common cause, either as part of a systemic disease or isolated to the nerves.

Causes : 1- Diabetes Mellitus . 2- Vasulitis :SLE, Rheumatoid arthritis , Behcet disease . 3- leprosy . 4- alcoholism . 5- Infection :HIV, CMV ,Hepatitis B & C virus . 6- sarcoidosis . 7- amyloidosis .

Investigations : Treatment : 1- NCS &EMG. 2-Investigations of the causes . 3- nerve biopsy . Treatment : According to the cause but if no cause is found, a trial of steroid may improve the neuropathy .

Polyneuropathy : This type of neuropathy start first in the distal lower limbs before the upper limbs, with sensory symptoms and signs of an ascending glove and stocking distribution ; all the nerves affected in the same time unlike mononeuritis multiplex in which there is a period between the affected nerves .

Guillain-Barré syndrome This syndrome of acute paralysis develops t 1-4 weeks after respiratory infection or diarrhoea (particularly Campylobacter ). In Europe and North America, acute inflammatory polyneuropathy is most commonly demyelinating (acute inflammatory demyelinating neuropathy AIDP). Axonal variants, either motor (acute motor axonal neuropathy or sensorimotor are more common in China and Japan. There is a predominantly cell-mediated inflammatory response directed at the myelin protein of spinal roots, peripheral and cranial nerves, possibly triggered by molecular mimicry between epitopes found in the cell walls of some microorganism s and gangliosides in the Schwann cell and axonal membranes followed by a complement-mediated destruction of the myelin sheath and the associated axon.

Clinical features: Distal paraesthesia and limb pains precede a rapidly ascending muscle weakness, from lower to upper limbs, m ore marked proximally than distally . Facial and bulbar weakness commonly develops, and respiratory weakness requiring ventilatory support occurs in 20% of cases. In most patients, weakness progresses for 1-3 weeks, but rapid deterioration to respiratory failure can develop within hours. On examination there is diffuse weakness with widespread loss of reflexes. An unusual axonal variant described by Miller Fisher comprises the triad of ophthalmoplegia, ataxia and areflexia. Overall, patients recover completely within 3-6 months, 4% die, and the remainder suffer residual neurological disability which can be severe. Adverse prognostic features include older age, rapid deterioration to ventilation and evidence of axonal loss on EMG.

Investigations : The CSF protein is elevated at some stage of the illness but may be norm al in the first 10 days. There is usually no or little rise in CSF cell number (a lymphocytosis of > 50 × 10 6 cell/L suggest a different diagnosis) .The protein may be increase leading to cytoalbumino dissociation . Electrophysiological studies are often normal in the early stages but show typical changes after a week or so . Investigation to identify an underlying cause, such as cytomegalovirus, mycoplasma or Campylobacter , requires a chest X -ray , stool culture and appropriate immunological blood tests. Antibodies to the ganglioside GQ1b are found in the Miller Fisher variant.

Management: During the phase of deterioration, regular monitoring of respiratory function (vital capacity and arterial blood gases) is required, as respiratory failure may develop with little warning and require ventilator support. Ventilation may be needed if the vital capacity falls below 1 L, but intubation is more often required because of bulbar incompetence leading to aspiration. General management to protect the airway and prevent pressure sores and venous thrombosis is essential. Corticosteroid therapy has been shown to be ineffective. However , plasma exchange and intravenous immunoglobulin therapy shorten the duration of ventilation and improve prognosis, provided treatment is started within 14 days of the onset of the symptoms ,but there is no advantage in combining the two treatments.

Acute axonal polyneuropathy : There is a rare variant of Guillain-Barré syndrome affecting the axon itself . Circulating antibodies to various peripheral nerve gangliosides are often found, this is more common with Cytomegalo virus infection .

Chronic Inflammatory demyelinating polyneuropathy: Causes : 1- idiopathic (autoimmune) is the commonest cause . 2- Diabetes . 3- Multiple myeloma . 4- vasculitis . 5- lymphoma . 6- Inflammatory bowel diseses. 7- Sarcoidosis and amyeloidosis . 8- HIV. 9- CMV and EBV.

Clinical Features : Chronic inflammatory demyelinating peripheral neuropathy (CIDP) presents with a relapsing or progressive generalized neuropathy . Sensory , motor or autonomic nerves can be involved but the signs are predominantly motor; also there is a variant type causes only motor involvement (multifocal motor neuropathy MMN).

Investigations : Treatment : The same as GBS but also include search for the cause. Treatment : CIDP usually responds to immunosuppressive treatment, corticosteroids, methotrexate or cyclophosphamide, or to immunomodulatory treatments (plasma exchange or intravenous immunoglobulin, I V I g); MMN is best treated by I V I g. Steroid will be given for 4-6 months followed by tapering dose with the initiation of other immunosuppressive drugs. The prognosis is variable and depend on the cause ,but the idiopathic type has the better outcome .

Hereditary Polyneuropathy : Many inherited disorders cause demyelinating peripheral neuropathies and one of the best known is Charcot-Marie-Tooth disease (CMT). Here the neuropathy produces distal wasting (inverted champagne bottle or stork legs), often with pes cavus, and a predominantly motor involvement. In 70-80% the cause is duplication of the PMP - 22 gene on chromosome 17 (autosomal dominant CMT type 1) . No treatment is available but physiotherapy may improve the motor deficit.