Neuromyelitis optica spectrum disorder patients have more pupillomotor symptoms than multiple sclerosis patients and have life-threatening autonomic dysreflexia, severe hypertension, sleep–wake cycle disturbances, and postural orthostatic tachycardia syndrome.
Neurological disturbances are a hallmark of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). Autonomic dysfunction is frequently present in these patients. However, due to its often vague symptomatology, patients and physicians can overlook it. A review in the Annals of Clinical Neurophysiology assessed the epidemiology, pathophysiology, clinical characteristics, and management of autonomic dysfunction in MS and NMOSD.
Proposed Pathophysiological Mechanisms of Autonomic Dysfunction
Two possible mechanisms of autonomic dysfunction in MS and NMOSD have been proposed: 1. lesions may disrupt the anatomical pathways of the autonomic nervous system, and 2. peripheral monocytes may affect interactions between the immune and autonomic nervous systems.
Autonomic Dysfunction in MS
Autonomic dysfunction occurs in 45–85% of MS patients. According to research, symptoms are observed in 75% of primary progressive MS (PMS), 60% of secondary PMS, and 30% of relapsing–remitting MS (RRMS) cases, and abnormalities on the autonomic function test (AFT) can be detected in 80%, 52%, and 30%, respectively.
- Bladder dysfunction and lower urinary tract symptoms are frequent among these patients, affecting approximately 30–75% in the early stages and >90% in the later stages. It is more common in PMS than in RRMS. The main treatment goals are to inhibit bladder hyperactivity and relax the sphincter.
- Gastrointestinal (GI) dysfunction occurs in 45–68% of patients, more commonly in PMS. Constipation and diarrhea are the most common, mainly attributed to pelvic floor dysfunction secondary to spinal cord lesions. Fecal incontinence often occurs in later stages. Upper GI symptoms, like reflux and delayed gastric emptying are also observed. Symptomatic treatment is recommended.
- Sexual dysfunction in the form of hypoactivity has a frequency of approximately 80% and is more common in RRMS. Appropriate drug therapy is indicated.
- Thermoregulatory dysfunction comprises cold sensitivity, anhidrosis, heat sensitivity during exercise, and hypothermia episodes.
- Cardiovascular autonomic dysfunction is observed in two-thirds of patients, while orthostatic hypotension is observed in half. These are more common in PMS. Other associations include arrhythmias and Takotsubo cardiomyopathy.
- Fatigue in MS occurs due to multiple factors, including autonomic dysfunction. Aberrations in vagal and sympathetic activity lead to perceived MS fatigue. Lifestyle changes and medications are helpful.
- Sleep disturbances are present in >50% of patients, more commonly in females. These are mostly attributed to muscle spasms, periodic limb movements, restless leg syndrome, nocturia, medications, and depression.
Frequency and Symptoms of Autonomic Dysfunction in NMOSD
Autonomic dysfunction is common in NMOSD, with a recent study showing a frequency of 74%. Life-threatening autonomic dysreflexia has been documented during relapses with cervical myelitis. Severe hypertension, sleep-wake cycle disturbances, bradycardia, and postural orthostatic tachycardia syndrome have also been observed. Recent studies have shown no significant difference in Composite Autonomic System Score 31 (COMPASS-31) scores between MS and NMOSD patients, with many NMOSD patients showing dysfunction in the GI, bladder, secretomotor, and vasomotor domains. However, NMOSD patients have a greater burden of pupillomotor symptoms than MS patients.
Kwon, S., & Min, J. (2023). Autonomic dysfunction in multiple sclerosis and neuromyelitis optica spectrum disorder. Annals of Clinical Neurophysiology, 25(1), 19–26. https://doi.org/10.14253/acn.2023.25.1.19