Chronic inflammatory demyelinating polyneuropathy (CIDP) is a generalized neuropathy with a progressive or relapsing course that often improves following immune therapy. Although most patients with CIDP have wide-spread symmetrical weakness and sensory abnormalities, some patients have symptoms and findings that are restricted to certain regions of the body or the illness affects the arms and legs in a very asymmetric or multifocal pattern. Such “regional variants” have been described rarely in midi including an unusual pattern of focal upper limb involvement, and are comparable to the regional syndromes that have been described in Guillain Barré Syndrome (such as the Fisher variant, oropharyngeal-bibrachial variant, pure sensory and pure motor forms, etc.). Many such cases of CIDP are easily confused with another form of immune neuropathy, termed multi-focal motor neuropathy an entity that has been distinguished from CIDP on the basis of asymmetric, upper limb weakness restricted to discrete motor nerve territories, nerve conduction findings of conduction block or other demyelinating abnormalities limited to motor fibers, few or no sensory abnormalities, and elevated anti-nerve (anti-GM1) antibodies directed against a constituent of the motor nerve fiber in the majority. When the initial or predominant features of CIDP are in the arms, the illness may also simulate other conditions, particularly compression of the nerves (entrapment neuropathy), inflammation of the brachial plexus (brachial neuritis), and dysfunction of multiple nerves due to disruption or inflammation of the blood vessels that supply blood flow to them (mononeuritis multiplex). The clinical, EMG, and treatment features of 10 patients with a focal, upper limb predominant type of CIDP were compared to 45 patients with more typical, generalized CIDP and to 13 patients with multifocal motor neuropathy.

Ten patients with a regional or multifocal neuropathy limited to the arms who fulfilled clinical and EMG research criteria for CIDP were identified during a 6 year period. There were 6 men and 4 women with an average age of 54 years and an average duration of symptoms of 10 months at the time of the initial evaluation. Nine had symptoms restricted to the arms or hands and one had severe weakness of both arms and the left foot. Numbness (10 patients), tingling (9), and weakness (8) were the first symptoms. Pain was a prominent initial complaint in 6 patients and was described as aching in the hand, arm, or shoulder in all, burning sensations in the forearm, hand, and fingers in 4, electrical, shock-like in 2, and shooting pain emanating from the shoulder in one. The ulnar nerve was most commonly affected and multiple nerves were involved in half of the patients. As the disorder progressed, the other arm became involved in 6 patients and 7 eventually acquired leg weakness.

Except for the regional and multifocal distribution of the symptoms and signs, there were few differences in the clinical features between CIDP patients with this regional variant and those with the more common, generalized form of CIDP. The proportion of patients who had sensory symptoms and signs was similar between the groups. Patients with regional arm involvement had less severe shoulder and hip girdle weakness, preserved tendon reflexes in the legs, and a normal gait. There were no statistical differences in numerous EMG parameters, and the proportion of patients who improved with treatment was virtually identical between the groups (60% in patients with the regional variant of CIDP vs. 66% in patients with generalized CIDP). However, there was a trend toward greater functional recovery in patients with generalized CIDP as measured by changes in the disability scores after therapy. In contrast, there were a number of clinical and laboratory features that distinguished the regional variant of CIDP from those with multifocal motor neuropathy. Patients with the restricted form of CIDP more frequently had sensory complaints (100% vs. 8%), abnormal sensory nerve conduction studies by EMG (73% vs. 10% of the sensory nerves tested), shorter duration of symptoms (10 vs. 28 months), and none had anti-GM1 antibodies (0% vs. 38%) There were no differences in the average age gender, distribution of weakness, disability score, frequency of an increased cerebrospinal fluid protein level, or response to treatment with IVIG (50% of patients with the regional variant of CIDP improved vs. 40% with multifocal motor neuropathy).

Our 10 patients, along with similar cases described by Saperstein and colleagues, have a chronic, progressive, multifocal demyelinating neuropathy that conforms to a regional variant of CIDP. The disorder begins with isolated or multiple mononeuropathies in the arms and most eventually develop generalized weakness with EMG studies demonstrating abnormalities characteristic of CIDP. Lewis and coworkers also described a similar condition in 5 patients with multifocal involvement of motor and sensory nerves of the arms. Many of these patients improve with steroids and other conventional therapies for CIDP. In contrast to patients with multifocal motor neuropathy, pain is a prominent symptom in patients with the regional variant of CIDP, all have complaints of sensory loss or tingling, sensory findings, and none have elevated anti-GM1 antibodies. Furthermore, sensory nerve action potentials are reduced or absent in virtually all patients, a salient finding that also distinguishes these cases from patients with multifocal motor neuropathy. Saperstein and colleagues highlighted similar clinical, laboratory, and EMG findings in their patients with multifocal, acquired, demyelinating motor and sensory polyneuropathy (MADSAM) and also concluded that their cases probably represented an asymmetric form of CIDP and should be differentiated from MMN.

The reason for a regional predilection for upper limb motor and sensory nerves in some patients with CIDP is uncertain, nonetheless, on the basis of clinical progression, electrodiagnostic studies and response to therapy, it is likely that these cases are variants in the spectrum of midi just as similar regional patterns are found among those with Guillain-Barré Syndrome.