Ataxia
The word Ataxia comes from Greek and means ‘absence of Order’. People suffering from ataxia have problems coordinating muscle movements. Often in the legs but also in the arms, eyes and in muscles used in speech. It is not a direct result of muscle weakness (atrophy) but a dysfunction in the sensory nerve inputs or motor nerve outputs.
Ataxia is quite common in multiple sclerosis but is also seen in conditions such as diabetic polyneuropathy, acute transverse myelitis, vacuolar myelopathy, tumour, or spinal cord compression.
There are three forms of ataxia, all of which can be seen in MS:
- Cerebellar Ataxia, this is caused by lesions in the cerebellum or in nerves that connect into it. Since the cerebellum is is responsible for synchronising voluntary muscle movement it might result in:
- Uncoordinated walking – gait ataxia
- Reduced control of range of movement – dysmetria
- Shaking when attempting fine movements – intention tremor
- Inability to control speech muscles – dysarthria
- Jittery eye movements – nystagmus
- Vestibular Ataxia, caused by lesions to the brainstem and the vestibular nuclei. It may also stem from damage to the 8th Cranial Nerve leading from the balance organs of the inner ear.
- Loss of Balance
- Dizziness, nausea, and vomiting – vertigo
- Jittery eye movements – nystagmus
- Sensory (Proprioceptive) Ataxia, dysfunction in position sensing (proprioceptive) nerve inputs. This means the brain is unable to determine the position of limbs.
- Loss of position sense
- Inability to detect vibrations
- An unstable stance – Romberg’s sign
- Friedreich’s ataxia. a genetic, inherited form of ataxia.
- characterized by an inherited mutation in the frataxin (FXN) gene leading to reduced levels of frataxin, a protein essential for life and cell survival.
The description of this symptom shows the commonality that exists across all the MS related symptoms. Myoclonus presents similar muscle control problems. Like MS ataxia is described as a symptom of an underlying disorder.
Ataxia is claimed to occur at the cell-level and shares this hypothesis with multiple sclerosis where dysfunctional mitochondria are suspected of being at play.
Anyone of any age can get ataxia, but certain types are more common in certain age groups. For example, people with Friedreich’s ataxia are usually diagnosed in childhood or adolescence.
References:
Multiple Sclerosis Encyclopaedia
What is Ataxia?
