Pediatric Movement Disorders - Ataxia

Workup

After listening to the history of the symptoms and examining the child, several steps may be taken, depending on the particular circumstances. The first question is whether the child has ataxia or some other condition that looks like ataxia. These other conditions include weakness, a sensory nerve problem, low blood pressure, dizziness, or other types of movement disorder. In particular, a child with leg weakness, spasticity, or dystonia may have an unstable and wide-based gait and may thus appear to have ataxia when in fact symptoms are due to an entirely different movement disorder.

If it appears that the child has ataxia, further studies often include laboratory tests and imaging studies. The most common initial laboratory tests include...

• Blood and urine for electrolytes, such as sodium, potassium, chloride, and bicarbonate
• Glucose
• Amino acids
• Organic acids
• Ammonia
• Copper
• Vitamin E

The most common initial imaging test is a brain magnetic resonance image (MRI) scan. This test enables the physician to look for structural abnormalities, stroke, or tumors. The MRI and initial laboratory tests are important to perform early as these tests may find causes for the ataxia that may require rapid treatment. In appropriate circumstances, it may also be important to test for toxins, medication overdoses, or heavy metal poisoning, particularly lead, mercury, and thallium.

If no cause for the ataxia is found after the initial set of tests, then further metabolic and genetic tests may be performed. The choice of these tests is based on the child's age, symptoms, and family history. The most commonly tested genetic disorders include the spinocerebellar ataxias or SCAs, of which there are many types, Friedreich's ataxia, and ataxia-telangiectasia (AT). If the child has myoclonus or myoclonic eye movements (opsoclonus) in addition to the ataxia, it is important to look for a neuroblastoma in the chest or abdomen, as these tumors may cause opsoclonus-myoclonus-ataxia syndrome.