Myasthenia Gravis: Case Study

Abstract

This study is a fictional case developed by Physical Therapy students from Queen's University to help with the understanding of the implications of a Myasthenia Gravis (MG) diagnosis on physical therapy assessment and treatment. The case study shows the clinical presentation, expectations of symptoms, comorbidities, and impairments of a patient diagnosed with MG. The case also presents some objective measures and treatment options based on individualities of the patient’s disease presentation.

Introduction

It is important for physiotherapists to take a comprehensive past medical history to screen for the many comorbidities that might be associated with the diagnosis of MG, including screening for red flags that might be related to a possible thymus tumour. It is also important to take into consideration the patient's medications, especially corticosteroid use, and the presence of possible underlying conditions. These findings can limit some treatment approaches and be contraindications or precautions for some manual therapy or exercise treatments.

Patients diagnosed with MG may present with several comorbidities. Since it is an autoimmune disorder, patients are at an increased risk for other autoimmune diseases such as Thymoma (thymus tumor) (Gilhus et al., 2015) (Gilhus, 2023), Systemic Lupus Erythematosus (Gilhus et al, 2015) (Misra et al., 2020) (Zhi-Feng Mao et al., 2011), Rheumatoid Arthritis (Zhi-Feng Mao et al., 2011) (Misra et al., 2020), and Diabetes Mellitus Type 1 (Gilhus et al, 2015), (Misra et al, 2020), (Gilhus, 2023). Some other common comorbidities include Hypertension (Misra et al, 2020), COPD (Misra et al., 2020) and the increased risk for respiratory infections due to muscle weakness and other issues related to prolonged corticosteroid use (Gilhus, 2023).

Pathophysiology

Myasthenia Gravis (MG) is an autoimmune disease affecting the antibodies to receptors at the neuromuscular junction, causing muscle weakness and fatigue. (Gilhus et al, 2015).

Presentation

This autoimmune disease is relatively uncommon with approximately 20 out of 100,000 individuals diagnosed with MG in the United States (Trouth et al., 2012). Reported prevalence in Ontario, Canada is similar with 32 out of 100,000 individuals (Breiner et al., 2016). In both Canada and the United States, there appears to be a greater incidence of younger women (<60 and <50 years old, respectively), diagnosed with MG (Trouth et al., 2012; Breiner et al., 2016). Whereas, in Canada and the United States, incidence appears to be greater in older men (>60 and >50 years old, respectively) (Trouth et al., 2012; Breiner et al., 2016).

Signs and Symptoms

The initial symptom that presents for two thirds of individuals is weakness of the extrinsic ocular muscles of the eyes (Trouth et al., 2012). This can present as ptosis, diplopia, and blurry vision (Trouth et al., 2012). The symptoms then typically progress to include other bulbar and limb muscles in approximately half of patients within two years (Trouth et al., 2012). One of the primary symptoms of MG is muscle fatigue and weakness, primarily skeletal muscle groups, that is exacerbated by activity and improves with rest (Trouth et al., 2012). Factors such as heat exposure, stress, and infection also worsen fatigue (Trouth et al., 2012). Muscle weakness can present as generalized or localized to oculomotor muscles, respiratory muscles, and laryngopharyngeal muscles affecting the ability to swallow (Gilhus, 2023).

Client Characteristics

The client is a 34-year-old, Caucasian woman, named Maya Stevens, who was recently diagnosed with Myasthenia Gravis. Mrs. Stevens reached out to her family doctor after experiencing a number of abnormal symptoms apart from her other diagnoses (Rheumatoid Arthritis and Hypertension). She was aware that a common comorbidity of these conditions is Myasthenia Gravis, and thought it was appropriate to seek medical advice. She was referred to Physical Therapy to address concerns, and to learn preventative techniques to avoid a decline in function and maintain future symptoms associated with the disease. Mrs. Stevens is a motivated, pleasant individual who is prepared to take a rehabilitative approach to her diagnosis.

Subjective

History of Present Illness (HPI)

Patient feels fine in the morning, but becomes more fatigued in the afternoon. She notices that her symptoms of MG, such as shortness of breath, muscular fatigue with exertion, complains of double vision, and right sided eye drooping which becomes worse when she is sick or stressed. She has been increasingly stressed while starting back at work after maternity leave, taking care of two young kids, and having a husband who works long hours. She has been taking care of many of the household duties and has a hard time picking up her kids.

Past Medical History (PMHx)

Mrs. Stevens was diagnosed with Rheumatoid Arthritis five years ago (currently well maintained and has not caused any problems) and hypertension nine months ago (currently well maintained and has not caused any problems) after giving birth to her second child. Mrs. Stevens was diagnosed with Myasthenia Gravis two months ago and has been experiencing an increase in symptoms.

Social History (SHx)

Patient lives in Kingston, Ontario in a bungalow with four steps to enter the home with a railing on both sides. She lives with her husband and two kids (one year and four years old). Mrs. Stevens works at a dental clinic as a receptionist and spends most of her day sitting, using the computer, and answering client questions or calls.

Health Habits (HH)

Does not smoke or use drugs. Has one glass of wine every evening (6-7 drinks/week) to wind down. Patient has been increasingly stressed after returning to work since leaving maternity leave, and has been partaking in a majority of the household and childcare duties while her husband works long hours in construction.

Current Functional Status (FnSt)

• bADLs: independent in most bADLs, but becomes fatigued from prolonged walking (greater than 20 minutes)
• iADLs: independent in the morning, but becomes more fatigued throughout the day making it more difficult to clean, cook meals, shop, drive, or do housework
• Physical Activity: difficulty finding time to exercise as she is often fatigued and tends to become more tired from exercise

Functional History (FnHx)

About a year before diagnosis, patient was fully independent in all bADLs, iADLs, ambulation, work activities, and family activities.

Objective

Observation

Upon observation, Mrs. Stevens was alert and oriented, making light conversation. Patient demonstrates some hoarseness of speech. She displays an apical breathing pattern. She demonstrates right-sided asymmetrical ptosis with exertion, as well as forward head posture.

Vital Signs

• Heart Rate (HR): 74 beats per minute
• Respiratory Rate (RR): 18 breaths per minute
• Blood Pressure (BP): 137/78
• Radial Pulse: strong and regular

Active and Passive Range of Motion

Range of motion was tested for all upper and lower extremity joints and demonstrated pain free active range of motion within normal limits bilaterally.

Strength

Manual Muscle Testing (MMT) was performed for U/E and L/E bilaterally (BL), as well as for the cervical spine.Upon assessment, Mrs. Stevens had the following MMT results:

• Cervical Spine: flexion & extension 3/5 BL; side flexion and rotation 4+/5 BL
• Shoulder: 3/5 flexion & abduction BL; 4/5 extension and adduction BL
• Elbow: 4/5 flexion & extension BL
• Wrist: 4+/5 flexion, extension; radial & ulnar deviation BL
• Handgrip: 4-/5 BL
• Hip: 3/5 flexion & abduction BL; 4-/5 extension & adduction BL
• Knee: 4+/5 knee flexion & extension BL
• Ankle: dorsiflexion 3+/5 BL; plantarflexion 4+/5 BL

Neurological Scan

A neurological scan was conducted to ... EXPLAIN

• Dermatomes: intact cervical and lumbar segments
• Myotomes: all myotomes affected, likely due to muscular weakness
• Cranial Nerves:
  • Positive CN V (Trigeminal) motor test, sensation intact
  • Positive CN VI (Abducens) test (cause for diplopia)
  • Positive CN X (Vagus) (dysphonia) motor
• Upper Motor Neuron Tests:
  • Babinski: Negative
  • Hoffman's: Negative
  • Clonus: Negative
• Lower Motor Neuron Tests - Deep Tendon Reflexes:
  • Triceps tendon (C7): Normal, Grade 2
  • Biceps tendon (C6): Normal, Grade 2
  • Patellar tendon (L3/L4): Normal, Grade 2
  • Achilles tendon (S1/S2): Normal, Grade 2

Balance

The Berg Balance Scale score was completed and Mrs. Stevens scored 41/56. This indicates a greater risk of future falls (42 and under), however, she is still within the category of being independent with no gait aid.