The myotonic muscle disorders compose a group of disorders characterized by muscle stiffness, pain, and sometimes weakness, which may be intermittent or constant. The primary periodic paralyses are rare inherited disorders associated with attacks of muscle paralysis. Depending on the…
In the evaluation of patients with suspected myopathy, molecular genetics has supplanted the need for electrodiagnostic (EDX) studies or muscle biopsy in many patients with inherited conditions. Moreover, in patients with suspected myopathy and no evidence of an inherited condition,…
Disorders affecting the neuromuscular junction (NMJ) are among the most interesting and rewarding seen in the electromyography (EMG) laboratory. These disorders are generally pure motor syndromes that usually preferentially affect proximal, bulbar, or extraocular muscles. They are confused occasionally with…
Sciatic neuropathies are uncommon in the electromyography (EMG) laboratory. When they occur, patients often present in a manner similar to that of peroneal neuropathy. Indeed, a foot drop from an early sciatic neuropathy may be difficult or impossible to distinguish…
The anterior rami of the L1–S3 roots come together to form the lumbosacral plexus, from which all major lower extremity nerves are derived. Disorders of the lumbosacral plexus are distinctly uncommon, but when they occur, they typically present with a…
Electromyographers are occasionally called on to evaluate the proximal nerves in the shoulder and arm. Isolated lesions of these nerves, including the suprascapular, axillary, musculocutaneous, long thoracic, and spinal accessory, are far less frequent than the common entrapment and compressive…
The brachial plexus is a complicated anatomic structure formed by the ventral rami of the lower cervical and upper thoracic nerve roots. Different fascicles from those roots intermix widely within the plexus to ultimately form all the nerves of the…
Radiculopathy is one of the most common diagnoses referred to any electromyography (EMG) laboratory. Even with the widespread use of magnetic resonance imaging, EMG continues to play an important role in the evaluation of radiculopathy. Although imaging studies usually are…
There are a heterogeneous group of motor neuron disorders that are rare but nonetheless important to recognize because they often mimic the presentation of amyotrophic lateral sclerosis (ALS). These often are referred to as atypical motor neuron disorders . They…
Electrodiagnostic (EDX) studies play a central role in the evaluation of patients with amyotrophic lateral sclerosis (ALS), the most common of all motor neuron disorders. Although described earlier by others, the French neurologist Jean-Martin Charcot is credited as naming the…