Marcus Gunn Syndrome and Multiple Sclerosis

One test which my neurologist, ophthalmologist, and primary care doctor each conduct during every office visit is the “swinging flashlight test.” You know the one. The doctor asks you to look ahead then shines a penlight first toward one eye, then the other, alternating quickly to observe your pupils’ response to light.

I strangely enjoy this test because I know that my pupils will show something unique. Something which proves that I have damage to my optic nerve. My pupils show a Relative Afferent Pupillary Defect (RAPD) or Marcus Gunn Sign.

What does the doctor look for during the “swinging light test”?

The pupils (the black centers of the eyes which dilate or constrict in response to light) are inspected for size, equality, and regularity. Did you know that the pupils will constrict or dilate when you look at objects far or near? They do, which is kinda cool.

More importantly, each pupil should constrict quickly and equally during exposure to direct light and to light directed at the other pupil (the consensual light reflex). Using the swinging light test, the doctor can test and observe the pupillary response to consensual light in order to determine if there is a defect present.

Normally, the pupil constriction does not change as the light is swung from eye to eye. When the light is moved quickly from eye to eye, both pupils should hold their degree of constriction.

What is a Relative Afferent Pupillary Defect?

The Afferent Pupillary Defect (APD) or Relative Afferent Pupillary Defect (RAPD) is an abnormal and unequal response in the pupils of the eyes when exposed to light. It basically demonstrates that one optic nerve transmits a different message to the brain than the other one. Testing for RAPD is a good way to implicate or rule out optic nerve damage such as is caused by optic neuritis.


My temporarily blinding case of optic neuritis in 2000 left my right eye impaired. It doesn’t register light in the same way as my left eye as the optic nerve has permanent damage. When the doctor shines the light in my left eye (the “good” eye), both pupils will constrict. This is normal. When the doctor quickly moves the light to my right eye (the “bad” eye), my pupils begin to dilate since the brain thinks that less light is coming in. This shows that there is damage to the corresponding optic nerve.

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MS Signs and Symptoms: What is Marcus Gunn Syndrome?

Nystagmus and Multiple Sclerosis

Nystagmus is a condition that causes the eyes to make quick, repetitive, uncontrolled movements — from side to side, up and down, or in a circular pattern — making the eyes appear to bounce around. The jerky motion may be triggered by optical stimuli or physical motion, or may occur at rest.

Nystagmus can be mild, occurring only when a person looks to the side, or it may be severe enough to impair vision. Nystagmus often makes it difficult to focus steadily on a fixed object.

What causes nystagmus?

Nystagmus can be an inherited condition, showing up in early childhood, or it can develop later in life due to an accident or illness. Nystagmus is often a symptom of an underlying medical problem, such as stroke, multiple sclerosis, or head trauma. Other causes of nystagmus include severe nearsightedness, albinism, inflammation of the inner ear, central nervous system diseases, and medication side-effects. Sometimes the cause may be unknown.


In persons with multiple sclerosis, lesions in the brainstem and cerebellum may interfere with the nerve signals that affect motion of the eyes causing nystagmus. According to the MS Foundation, approximately 35 percent of individuals with multiple sclerosis may develop nystagmus. Abnormal gaze-holding mechanisms, vestibular imbalance, and impaired fixation are the most common causes of nystagmus in multiple sclerosis.

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MS Signs and Symptoms: What is Nystagmus?

MS Pain: What is the MS Hug?

Pain is not a symptom of multiple sclerosis, right? Wrong. That has got to be one of the more frustrating myths for those of us living with MS. Pain in MS can show up as neuropathic pain or musculoskeletal pain. A particularly disturbing type of pain in MS that can sometimes feel like a boa constrictor is squeezing the breath out of you has commonly been called the MS hug.

Neuropathic pain

Symptoms of MS stem from damaged myelin (the coating that protects nerves) that impacts proper nerve function and health. Neuropathic pain can be caused by disrupted nerve signals. Symptoms of neuropathic pain may include abnormal sensations — tingling, numbness, skin crawling, itching, burning, or prickly sensations — which are called paresthesias. These can be acute or chronic, severe or mild, painful or just plain weird.

Musculoskeletal pain

In MS, disrupted nerve signals and overly sensitive motor neurons can lead to spasticity and/or painful muscle spams. Musculoskeletal pain caused by muscle spams, muscle weakness, physical stress on joints, or poor coordination are commonly associated with MS. These pains may be acute or chronic. When they show up suddenly, last only a brief period of time, and disappear rapidly, they are called paroxysmal symptoms. Paroxysmal symptoms may occur once or repeat over a longer period of time. If they show up repeatedly, that might be a sign of an MS relapse.

Treatment for MS pain

Common pharmacological management of neuropathic pain in MS includes anti-seizure drugs, corticosteroids, anti-spasticity drugs, or benzodiazepines. Antidepressant agents and opioids may help to modulate the experience of pain. Musculoskeletal pain may respond to physical therapy, stretching, spasticity medications, and conventional painkillers such as ibuprofen.

The MS hug: Definition and causes

The MS hug is a highly unpleasant, painful banding sensation that occurs anywhere around the torso. Some people in the online community have referred to the MS hug as the “Squeeze o’ Death.” Symptoms of the MS hug can show up anywhere on the torso, on one side or the other, or circling all the way around the body. The pain can range from mild numbness or tingling to excruciatingly sharp pain or pressure. Each person’s experience is unique and may even differ from one episode to the next.

Explanations of the cause of the MS hug vary. The pain may be neuropathic in origin such as dysesthesia (which is basically a really bad paresthesia). The pain might stem from extreme spasticity in the intercostal muscles of the rib cage. There are three layers of muscle fibers in the intercostal muscles that connect the ribs and assist with breathing. If these muscles are involved, symptoms may include chest tightening, difficulty breathing, and limited mobility.

What to do if you have the MS hug

If you suddenly experience chest pain or asthma-like symptoms, or you feel like a big snake is trying to squeeze the life out of you, don’t assume that it is your MS. Seek medical attention immediately. There may be another cause of your symptoms or pain. It’s better to err on the side of caution when your health is concerned......

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What is the MS Hug?

Why Does the Neurologist Tap My Finger?

The neurologist is looking to see if there is a finger flexor response.  The finger flexor response is demonstrated by a sudden flexing of the thumb and/or index finger.  There are two ways to cause this response:

• The doctor snaps or flicks the nail of the middle or 4th finger.  A positive finger flexor response elicited in this manner is known as the Hoffmann reflex or sign.
  
• The doctor holds the middle finger while partially flexing it between his/her finger and thumb, then taps or flicks the underside of that finger.  A positive finger flexor response elicited in this manner is known as the Trömner sign.
  

What causes the thumb to flex?

The finger flexor response (Hoffmann relex or Trömner sign) is somewhat similar to the Babinski sign in that it is suggestive of a lesion or impingement along the corticospinal tract.

What is the corticospinal tract?

Very long nerve axons which originate in the part of the brain called the cerebral cortex travel through the brainstem, cross over at the top of the cervical spine and travel down each side of the spinal cord. This path is the corticospinal tract which is sometimes called the pyramidal tract since the area where the crossover of nerves occurs has a pyramid-like shape.

Corticospinal tract neurons are referred to as “upper motor neurons” but they do not control muscles directly. Neurons in the ventral horn that directly innervate (or stimulate) muscle are called lower motor neurons.  It is damage in lower motor neurons which causes atrophy of muscle, while damage in upper motor neurons does not.

How do the Hoffmann or Trömner signs differ from the Babinski sign?

Each of these signs indicate damage in the corticospinal tract. The Babinski sign indicates damage anywhere along the corticospinal tract. However, the Hoffman and Trömner signs are a bit more specific in that they indicate a lesion or damage above the C5 or C6 level of the cervical spine.

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MS Signs and Symptoms: What is the Hoffmann Reflex?