Trauma can wreak havoc to any patient well beyond the musculoskeletal system; and in particular can complicate the healing process in patients suffering from pre-existing neuromuscular conditions before a traumatic insult. Trauma that is superimposed on a pre-existing, though well-maintained, neuromuscular condition can result in a significant increase in the neuro-muscular symptoms. In other cases, patients with no known symptomology of a dormant and asymptomatic pre-existing condition can be diagnosed with a neuromuscular condition that was triggered by the “awakening” from sudden trauma. One of these neuromuscular conditions is Myasthenia Gravis (MG), an autoimmune disease of the neuromuscular system that is known to affect all races, both genders, and multiple age groups.[1]
What is Myasthenia Gravis (MG)?
The name “Myasthenia Gravis” literally translates into “grave muscle weakness.”[2] It is an autoimmune neuromuscular condition that causes varying degrees of weakness of the voluntary muscle groups. While the most common sign of MG is often a drooping eyelid, it can also result in blurred or double vision, slurred speech, difficulty chewing and swallowing, weakness in the arms and legs, and difficulty breathing.[3] MG causes muscle weakness by interrupting the normal communication between nerves and muscles at the “neuromuscular junction” (where nerve cells connect with the muscles they control). Nerve receptors that should allow neurotransmitter chemicals to contract muscles normally are instead blocked, altered, or destroyed by antibodies, causing as much as an 80 percent reduction in the number of receptor sites.[4] Testing for MG can include blood tests, nerve conduction studies, and single fiber electromyography (EMG).
Trauma and Myasthenia Gravis (MG)
Several case studies have helped explain the role trauma can play in patients with MG. One study examined the role of trauma in a patient with stable MG (no symptoms) who then suffered a spinal cord injury as a result of a motor vehicle collision. [6] Immediately after the collision, the patient’s neurological examination revealed markedly reduced muscle strength in all four limbs, absence of sensation below the C4 dermatome, and absence of tendon reflexes. Cervical spine MRI showed posterior bulging of the intervertebral disc at C3-4, C4-5, and C5-6, with compression of the cervical spinal cord. Following a laminectomy and plate fixation for cord decompression, the patient’s neurological function and muscle strength all improved. One week later, the patient developed a urinary tract and respiratory tract infection, along with significant weakness of the eye muscles and in all four limbs. However, sensory function was normal. Cervical spine MRI showed no cause for the symptoms and the worsening of the patient’s MG was confirmed through blood testing. The authors of the study noted MG relapses are known to be triggered by factors including infections, emotional stress, and increase in body temperature, among others.
A second case study reported on the effects of a concussion, whiplash injury, and sternal fracture, all from a motor vehicle collision, on a patient with no pre-existing MG symptoms.[7] Within two months after the collision, the patient developed blurred vision, a drooping upper eyelid, double vision, difficulty swallowing, and weakness of the arms and legs. MRI of the cranium was normal. The patient did not have risk factors commonly associated with MG. The patient consulted with a neurologist and laboratory analysis helped confirm the diagnosis of Myasthenia Gravis. The authors of the study concluded that the relatively short onset of MG symptoms after the motor vehicle collision made it likely that the sternal fracture awakened previously dormant and asymptomatic MG as part of the body’s reaction to the inflammatory process.
Other similar case studies have also related a link between the onset or worsening of MG and trauma.[8]
These studies underscore the importance of evaluating a patient as quickly as possible after injury to properly reach a differential diagnosis(es). Unfortunately, insurance companies confronted with less common conditions like MG can quickly dismiss injury claims by erroneously labeling them as “pre-existing conditions” that result from something other than trauma. Other times, insurance companies unfamiliar with this condition will improperly assume a patient previously suffering from MG was experiencing pain, as opposed to muscle weakness, and use this as a basis to deny an injury claim. For these reasons, it is important for patients to consult with knowledgeable legal counsel well-informed on medical conditions who can effectively assist them through the claims process after an injury.
[1] myasthenia.org/WhatisMG.aspx
[2] www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm#3153_5
[3] myasthenia.org/WhatisMG.aspx
[4] myasthenia.org/WhatisMG.aspx
[5] www.hopkinsmedicine.org/healthlibrary/conditions/nervous_system_disorders/myasthenia_gravis_85,P07785/
[6] Che-Sheng Lin, MD, et al. “Myasthenia Gravis with Superimposed Spinal Cord Injury: A Case Report” J Rehabil Med 2008; 40: 684-686.
[7] Jens A. Petersen, et al. “Autoimmune Myasthenia Gravis after Sternal Fracture” Case Reports in Neurology; 2012; 4:20-22.
[8] Russell Lane, et al. “Myasthenia gravis precipitated by trauma: Latent myasthenia and the concept of “threshold” Neuromuscular Disorders; 2009; 19 (11): 773-5
