Living with multiple sclerosis introduces you to many different, often bizarre, symptoms. Numbness, itching, weakness, pain, spasticity, cognitive problems, depression, anger, vision changes, urinary urgency, constipation, paralysis, inappropriate laughing or crying, fatigue, insomnia, daytime sleepiness, euphoria, balance problems, foot drop, heat sensitivity, sexual dysfunction; the list can go on and on.
For example, do you ever sense that lights are too bright or sounds are too loud when they seem normal to everyone else? Do you jump at the drop of a pin? If so, you might be suffering from increased sensitivities to stimuli. There are a couple of conditions that could explain your experience.
Multiple sclerosis is associated with malfunctioning nerves in the central nervous system (CNS) caused by demyelination. That means the protective lining around your nerves has become damaged or is missing. Myelin helps nerve impulses travel along the CNS between the brain and body. Sometimes, a lack of myelin causes a misfiring of nerve impulses which might interrupt, subdue, or amplify the messages. It’s the misfirings that contribute to symptoms.
What is hyperacusis?
Hyperacusis is commonly defined as a heightened, abnormal sensitivity or intolerance to ordinary, everyday sounds. Some 8-15 percent of the general population suffers from it. “Normal” sounds for you might be perceived as outrageously LOUD and painful to me. The effects of hyperacusis can range from mild to severe. But not all hyperacusis is the same; a recent literature review suggests there are four forms:
- Loudness hyperacusis: moderately intense sounds are judged to be very loud. A single ear may be affected or only some sounds or tonal frequencies involved.
- Annoyance hyperacusis: a negative emotional reaction to sounds which may be specific to particular sounds or groups of sounds, manifesting as irritation, anxiety, or tension.
- Fear hyperacusis: an aversive response to sounds that results in an anticipatory response and avoidance behavior, often impairing one’s ability to enjoy normal social, recreational, or vocational activities.
- Pain hyperacusis: pain is experienced at much lower sound levels and may be reported as a stabbing pain in the ear or the head. It is not clear whether pain hyperacusis reflects a lowering of the normal pain threshold (typically around 120 decibels) or a different process or mechanism altogether.
What is myoclonus?
Myoclonus refers to a sudden, involuntary jerking of a muscle or group of muscles. It describes a symptom, not a diagnosis or disease. Myoclonic twitches or jerks may occur spontaneously or be induced by stimulus. The jerks may result from sudden muscle contraction or muscle relaxation. Myoclonus can vary in intensity, frequency, or location. Most cases of myoclonus result from disturbances in the central nervous system.
Myoclonus may be as innocuous as a hiccup or “sleep starts” that some people experience while drifting off to sleep. Severe causes of myoclonus may be more persistent or widespread and distort movement, severely limiting a person’s ability to eat, talk, or walk.
There are several forms of myoclonus, but one which is particularly relevant for people with MS is stimulus-sensitive myoclonus. It can be triggered by a variety of external stimuli, including noise, movement, and light. A surprise or an unexpected event may increase the sensitivity of the individual.
Which makes me jump more: stimulus-sensitive myoclonus or hyperacusis?
Both conditions can contribute to an exaggerated “startle reflex,” and I’ve personally experienced either one at different times. My ears seem to be extra sensitive to sounds and a simple laugh of a child can feel like an icepick hammered into the center of my head, which understandably makes me jump. There are times that a phone ringing makes the muscles at the base of my head suddenly jerk to the right. No one else seems to notice, but I can feel it.
When symptoms of hyperacusis and myoclonus overlap, sounds can become painful, loud, and startling. Treatment for hyperacusis consists coping skills and acoustic therapy aimed to reduce a person’s reactions and sensitivity to sounds. Treatment of myoclonus may include medications such a clonazepam that have a tranquilizing effect. I’ve found that meditation, and earplugs, can help.
Tyler RS, Pienkowski M, et al. A review of hyperacusis and future directions: part I. Definitions and manifestations. Am J Audiol. 2014 Dec;23(4):402-19.
Weber H, Pfadenhauer K, Stöhr M, Rösler A. Central hyperacusis with phonophobia in multiple sclerosis. Mult Scler. 2002 Dec;8(6):505-9.