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Motor Neuron Diagnosis

Diagnosing motor neuron disorders (MNDs) is a complex and extensive process. Motor neuron disorders are characterized by respiratory muscle weakness, emotional instability, and muscle weakness and atrophy. Motor neuron disorders are caused by progressive degeneration of anterior horn cells, corticospinal tracts, bulbar motor nuclei, or a combintation. Disorders are most common among men in their 50s.

  1. Signs and Symptoms

    • MNDs are classified in categories of upper and lower dependent upon the area of motor neurons that they affect, and symptoms vary widely dependent upon the affected category. Upper MNDs usually manifest in the mouth or throat and then spread out to the limbs, resulting in stiffness and awkward movement. Lower MNDs are usually expressed as facial weakness, dysarthria and visible muscle twitches. Other symptoms of lower MNDs include muscle cramps that usually begin in the hand, foot or tongue as well as general muscle weakness and atrophy. It is important to determine the category of the MND before attempting a treatment.

    Amyotrophic Lateral Sclerosis

    • Amyotrophic lateral sclerosis (ALS), an upper and lower MND commonly known as Lou Gehrig's disease, presents itself as a series of random, asymmetric symptoms such as hand muscle weakness that progresses to the shoulders and lower limbs. According to the Merck Manual, death usually occurs as a result of failing respiratory muscles and a staggering 50 percent of patients die within three years of the onset. Twenty percent can go on to live five years after the onset while only 10 percent live 10 years after onset.

    Progressive Bulbar Palsy

    • The Merck Manual states that progressive bulbar palsy manifests as primarily affecting the nose and throat. Symptoms will cause an increasing difficulty in swallowing, talking and chewing as well as causing weakness in facial muscles. Respiratory complications with PBP typically result in death in less than three years after the initial onset.

    Progressive Muscle Atrophy

    • Progressive muscle atrophy is a more benign MND that can manifest itself at any age. Random muscle twitches can indicate early onset and the disease usually progresses over a longer period of time, manifesting as generalized muscle weakness and wasting. Patients may survive 25 or more years with this condition.

    Diagnosing a MND

    • Before diagnosing a MND, other possibilities will need to be ruled out, such as: neuromuscular transmission disorders, thyroid and adrenal disorders, electrolyte abnormalities, myopathies, polymyostosis, dermatomyositis, as well as various infections such as Lyme disease or Hepatitis C. Bloodwork and laboratory testing can determine whether the symptoms are being caused by one of the aforementioned issues. Once other possibilities have been ruled out, the patient will need to undergo a series of electrodiagnostic tests as well as an MRI of the brain and possibly cervical spine. Considered to be the most useful form of electrodiagnostic testing is needle electromyography (EMG). EMGs will show fasciculations and fibrillations indicating the presence of a MND. If no evidence is found from the EMG, then a MRI of the cervical spine will be taken in addition to the brain MRI in order to check for structural lesions.

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