Neuromuscular disorders are diseases that affect the peripheral nervous system in any location from the anterior horn cells in the spinal cord, peripheral nerves, neuromuscular junction (NMJ), to the muscles. Identifying and treating neuromuscular disorders is of special concern for hospital providers, as patients with these conditions may develop acute episodes of generalized weakness, leading to respiratory failure and difficulty weaning from mechanical ventilation. The following discussion will focus on identification and management of various neuromuscular disorders. Additional discussion of classification and localization will enable providers to better diagnose the disease process. The remainder of the chapter will focus on causes of acute weakness and management of these disorders in acute and hospital settings.
An otherwise healthy 36-year-old man developed Paresthesias in the soles of both feet 2 weeks after recovering from a mild upper respiratory tract infection. Over the course of the next 4 days, the paresthesias gradually ascended to the level of both knees and developed in his hands and forearms as well. In addition, he developed difficulty with dexterity and trouble walking due to progressively worsening weakness in all four extremities. He presented to an emergency department (ED) where he was found to have mild bifacial weakness, diffuse weakness in his arms and legs, absent vibratory sensation to the level of his knees, and absent muscle stretch reflexes throughout. A lumbar puncture demonstrated no white blood cells but an elevated protein level. While in the ED he developed dyspnea and was intubated and placed on mechanical ventilation. He was admitted to the intensive care unit (ICU) for further management.
CLASSIFICATION OF NEUROMUSCULAR DISORDERS1,2
Neuromuscular disorders are diseases that affect the peripheral nervous system. These disease states can affect any location from the anterior horn cells in the spinal cord, peripheral nerves, neuromuscular junction (NMJ), to the muscles.
Motor neuron disorders (MND)
MNDs are a group of progressive disorders caused by dysfunction of the anterior horn cells. Motor neurons are necessary in controlling voluntary muscle activity including speaking, swallowing, breathing, and ambulation. MNDs occur in both adults and children, and may be present at birth in children with inherited or familial forms of the disease. Although some forms of MNDs are inherited, the majority are sporadic. MNDs are often classified as to whether they lead to dysfunction of upper motor neurons (UMNs), lower motor neurons (LMNs), or both.
Acquired disorders of the lower motor neuron include poliomyelitis and West Nile virus infection. Most patients who are infected with these viruses are usually asymptomatic; however, a minority will develop neurological involvement. Patients may present with nonspecific symptoms such as headache, myalgias, malaise, and sore throat. A select number of patients with poliomyelitis develop severe neck, back and muscle pain along with asymmetric muscle weakness and atrophy. West Nile virus can lead to neuroinvasive disease causing encephalitis ...