Plexopathies

, Ali T. Ghouse² and Raghav Govindarajan³

(1)

Parkinson’s Clinic of Eastern Toronto and Movement Disorders Centre, Toronto, ON, Canada

(2)

McMaster University Department of Medicine, Hamilton, ON, Canada

(3)

Department of Neurology, University of Missouri, Columbia, MO, USA

Plexus lesions often present a clinical and electrodiagnostic challenge. Electrodiagnostic techniques can localize a lesion to a plexus and can also provide evidence for peripheral nerve or root lesions that might produce similar symptoms. Electrodiagnostic studies can define the pathophysiology and severity of a plexopathy and can differentiate root evulsion or plexopathy related to compressions (such as from a tumor or hematoma) from plexopathy as an effect of radiation therapy. Follow-up studies show the course of the plexus injury, aiding in management and in determining prognosis.

The differential diagnoses of plexopathies are mononeuropathies and radiculopathy. It is often necessary to study all the main sensory and motor nerves that can be studied in an extremity. Extensive needle electromyography (EMG) is also required. Long latency reflexes may also provide useful information. Contralateral studies are also necessary, especially if the symptoms are bilateral or when the contralateral limb can serve as a control.

Brachial plexopathy causes weakness, sensory loss, and the loss of tendon reflexes in body regions innervated by nerves in the C5-T1 segmental distribution. The clinical diagnosis is confirmed through electrodiagnostic studies (i.e., EMG).

Lumbar plexopathy causes weakness, sensory loss, and reflex changes in regions innervated by nerves in the spinal L1-L4 segmental distribution. This results in weakness and sensory loss in the obturator- and femoral-innervated territories.

Sacral plexopathy produces the same abnormalities as lumbar plexopathy, in segments L5-S3, resulting in weakness and sensory loss in the gluteal (motor only), peroneal, and tibial nerve territories.

Brachial Plexus Anatomy

The brachial plexus is a somatic plexus formed by the ventral rami of the lower four cervical nerves (C5–C8) plus the first thoracic nerve (T1). It innervates all of the muscles of the upper limb, with the exception of the trapezius and the levator scapula. The plexus supplies all of the cutaneous innervation of the upper limb, with the exception of the area of the axilla that is supplied by the intercostobrachial nerve. This area is just above the point of the shoulder (supplied by supraclavicular nerves) and the dorsal scapular area (supplied by cutaneous branches of the dorsal rami).

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