Understanding the Cerebellum in Health and in MS

Coloured light micrograph of a section through the highly-folded cerebellum of the brain
STEVE GSCHMEISSNER/Science Photo Library/Getty Images

Your cerebellum is the lower-back region of your brain, consisting of two hemispheres (halves). It’s located behind the top part of your brainstem, where your spinal cord connects with your brain. You may be surprised to learn that although your cerebellum makes up only about 10% of your brain’s total weight, it contains roughly 50% of its message-transmitting nerve cells.

So much nervous-system involvement in so little space! That suggests that your cerebellum has a big job, and so it does.

Your cerebellum helps you with coordination (moving the parts of your body smoothly and purposefully), posture, and balance as well as speech and a number of important mental processes. It does this by receiving information from your sensory systems (for example, your eyes and ears, your sense of smell and taste, and your sense of touch), your spinal cord, and other parts of your brain.

What Happens If the Cerebellum Is Damaged?

Movement Problems. When your cerebellum is damaged, nerve cells break down and die. A disease or condition that damages your cerebellum — for example, multiple sclerosis (MS) — can cause poor balance and tremors (shaking) and slow down your ability to move.

  • Loss of control of the ability to move your body the way you want (voluntary movement) is called ataxia.
  • A person with cerebellar damage is likely to walk unsteadily, even clumsily. He or she may look “drunk” even though that isn’t the case.

Cognitive Impairment. There’s more that can happen if your cerebellum is damaged: You may have cognitive impairment (reduction in your conscious mental activities, such as thinking, learning, and remembering) as well.

About 40% to 65% of people with MS have cognitive impairment, making it a core symptom of the disease. In approximately 11% of that group, the cerebellar symptoms are the strongest indication that a person has MS.

Generally speaking, MS mainly affects such cognitive functions as memory, mental “processing speed,” executive tasks (for example, the ability to plan ahead or concentrate despite distractions), attention, and concentration.

You should also be aware that, in MS patients, fatigue, depression, and physical disability can make problems with memory and processing speed worse.

The Cerebellum in Advanced MS

In a person with advanced MS, movement problems together with spasticity (muscle tightness or stiffness) may cause severe physical disability. In addition, the ongoing damage to the cerebellum may lead, for example, to slurred speech, “scanning” speech (slow forming of words and pauses between words or even syllables), and the Charcot triad, consisting of scanning speech, nystagmus (rapid and involuntary eye movements), and intention tremor.

  • Intention tremor is involuntary shaking of an extremity during visually guided, purposeful (intentional) activity, such as reaching for an object on a table. A person with MS who has intention tremor will often “overshoot” or “undershoot” the target; this is called dysmetria.
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Article Sources
  • Weier K, Banwell B, Cerasa A, et al. "Role of the cerebellum in multiple sclerosis." Cerebellum. 2015;14:364-374.  
  • “Balance: balance problems in MS.” Multiple Sclerosis Association of America (2013). 
  • Apatoff BR. “Multiple sclerosis (MS).” Merck Manual, professional version (2016). 
  • “Cerebellum.” Healthline.com (2015).
  • Hain TC. “Cerebellar disorders.” Northwestern University: Chicago Dizziness and Hearing (2015).