From the Guidelines
For a 41-year-old female with diffuse back spasms and a history of myotonia congenita, I strongly recommend starting with mexiletine 150 mg twice daily, which can be gradually increased to 200 mg three times daily as needed for symptom control, while closely monitoring cardiac function due to the potential cardiac effects associated with myotonic dystrophy, as highlighted in the American Heart Association's scientific statement 1.
The patient's history of myotonia congenita suggests a possible diagnosis of myotonic dystrophy, which is a heterogeneous group of inherited neuromuscular diseases characterized by muscle weakness and myotonia, as described in the study 1. Given the cardiac manifestations present in approximately 80% of myotonic dystrophy type 1 patients, it is crucial to monitor cardiac function closely while managing the patient's symptoms.
Key considerations in managing this patient's condition include:
- Starting with mexiletine 150 mg twice daily, which can be gradually increased to 200 mg three times daily as needed for symptom control
- Alternative medications such as phenytoin 100 mg three times daily or carbamazepine 200 mg twice daily, which work through similar mechanisms
- Using cyclobenzaprine 5-10 mg three times daily for 7-10 days to provide relief for acute back spasms
- Implementing physical therapy focusing on gentle stretching and strengthening exercises for long-term management
- Avoiding triggers like cold temperatures, certain medications, and strenuous exercise without proper warm-up
Regular monitoring of cardiac function is necessary due to the potential cardiac effects associated with myotonic dystrophy, as highlighted in the American Heart Association's scientific statement 1. By prioritizing the patient's cardiac health and managing her symptoms effectively, we can improve her overall quality of life and reduce the risk of morbidity and mortality.
From the FDA Drug Label
Cyclobenzaprine hydrochloride tablets are indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions Cyclobenzaprine hydrochloride tablets have not been found effective in the treatment of spasticity associated with cerebral or spinal cord disease, or in children with cerebral palsy.
The patient has a history of myotonia congenita, which is a muscular disorder. The drug label indicates that cyclobenzaprine is used for relief of muscle spasm associated with acute, painful musculoskeletal conditions. However, it does not specifically address myotonia congenita.
- The label does mention that the drug is not effective in the treatment of spasticity associated with certain conditions, but myotonia congenita is not explicitly mentioned.
- Given the lack of direct information, cyclobenzaprine may not be the best choice for this patient, as its effectiveness for myotonia congenita is unknown 2.
From the Research
Myotonia Congenita and Back Spasm
- Myotonia congenita is a genetic disorder characterized by muscle membrane hyperexcitability caused by reduced sarcolemmal chloride conductance due to mutations in CLCN1 3.
- The disorder may lead to symptoms of muscle stiffness, pain, fatigue, and weakness, which can be exacerbated by back spasm.
- In patients with myotonia congenita, back spasm can be a significant source of discomfort and disability.
Treatment Options
- Botulinum toxin has been investigated as a potential treatment for myotonia congenita, but it has been shown to be ineffective in reducing rigidity and pain 4.
- Mexiletine, a sodium channel blocker, has been shown to be effective in reducing stiffness and improving quality of life in patients with non-dystrophic myotonias, including myotonia congenita 5, 6.
- Conventional therapies such as lifestyle modifications, nonsteroidal anti-inflammatory drugs, physical therapy, and cognitive behavioral therapy may also be used to manage back pain associated with myotonia congenita 7.
Management of Back Spasm
- A detailed history and physical examination are necessary to exclude other causes of back pain and to develop an effective treatment plan.
- Symptomatic treatment with mexiletine or other sodium channel blockers may be considered, as well as educating patients about potential anesthetic complications 6.
- Imaging and specialist referral may be indicated if back pain persists for greater than 6 weeks despite conventional therapies 7.