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Ataxia in Children

Clinical approach to the child with ataxia. The true definition of ataxia is "Itís a disturbance of coordination and rhythm and volitional and postural movements ataxia, difficulty walking, trouble walking." And the neuroanatomic substrates are the cerebellum, the midline structure of the vermis, and the hemispheres and its major inputs. One of the important things in neurology, as you try to localize it, is when you have long and complicated circuits involved, the lesion could be in many parts of that and give you a common sign. So you have to do careful evaluation to localize it. The neuroanatomic correlation here is 

Whether there is dysmetria. Now not only can you do finger-to- nose to do hypotonia of limb, you can also see the dysmetria simply. You could simply ask the patient to rapidly look at your nose and your finger, holding your finger aside. In a normal person it will be very accurate. One shot. The eyeball movement. If the eyeball overshoots and corrects, or under shoots and corrects, it could be cerebellar. Then there could be dyssynergia, dysdiadochokinesia, thatís rapid alternating movements. There could be intention tremor in the affected side. The sensory disturbances can give you ataxia because, as I told you, itís not an

Acute ataxia in a child. What is the differential? Well, itís not uncommon to have postinfectious involvement of the cerebellum. This can occur after varicella, EBB, Mycoplasma, a variety of these. Intoxication should be early in your differential, particularly alcohol, sedative hypnotics. Maybe the child comes from a family where somebody else has a seizure disorder and Dilantin was lying around, that type of thing. Occult neuroblastoma, the so-called opsoclonus-myoclonus syndrome, frequently has ataxia 

Intermittent ataxia that fluctuates, comes and goes, is often due to an inborn error of metabolism. You could see that in maple syrup urine disease. These people often have other elements in the history. The genetics people will talk to you more about it. But they may have intermittent encephalopathy with minor illnesses, and so on. These people have difficulty handling branched chain amino acids. Such as valine, leucine, isoleucine and therefore require special dietary management. Some of the urea cycle defects can also lead to intermittent encephalopathy, vomiting. The ammonia is elevated and they are treated again with protein restriction, sometimes benzoate or arginine may be given to facilitate excretion of excessive ammonia. Hartnupís disease is one

Mitochondrial disorders: again, it is a large topic in itself. This morning when we talked about myopathies I showed you some mitochondrial pictures. We mentioned MELAS at that time as well. And you may have encountered kids with Layís syndrome, early onset seizures, mental retardation, hypotonia and nystagmus. All these people could have ataxia. Basilar migraine and variants could be intermittent. Then there is a rare entity called "familial acute intermittent ataxia". Now it is called one of the 

Here is a cerebellar astrocytoma. You can see in the location and you can also see it has a cystic component. Thatís the axial view and hereís a sagittal view showing the cystic cerebellar component with obstruction of some of the aqueductal areas.

Friedreich ataxia, an important disease. Also called spinal cerebellar degeneration. And this is a multi-system disorder with first decade onset. It is autosomal recessive. What we have learned more recently is that, in people who are homozygous and have both alleles, there is a triplet repeat expansion. I alluded to this earlier when we talked about congenital myotonic dystrophy. We have a variety of diseases now that belong to this family. You will probably hear about this more from the genetics people but the idea is that in the decade we are learning that a variety of bad diseases, particularly those with anticipation for successive generations get worse, occur from triplet repeats. Where a sequence of three nucleic acids, like CTG - normal people have, for example, 15 repeats in a particular site. The next generation goes to 40 and they are not so well. The following generation has 200 repeats and they get very sick. We learned about this first in hunting for the gene for Huntingtonís disease. Now we find that itís a classic paradigm of disease. So itís involved in several of them, including Friedreich ataxia. So we call them "unstable triplet repeats". Meaning, every body has there repeats but they get expanded with successive generations. Friedreichís is truly

Ataxia telangiectasia is another one that is an inexorably progressive disease. Again, it is autosomal recessive. The gene has been cloned. We know now that the defect here is in DNA repair and the onset of the disease is around 1-3 years. There are telangiectasias that are easiest to see in the conjunctiva and in the pinna of skin. Again, they present with dysarthria, ataxia and a very distinctive early finding is oculomotor apraxia. And you are saying, "What is that?" It simply means they cannot initiate

Bassen-Kornzweig syndrome is another interesting disease that can cause ataxia -and this again is kind of related to something Marvin Ament told you speaking of vitamin deficiencies - itís called Bassen-Kornzweig syndrome. Most of us just call it a-beta lipo-proteinemia, or more commonly, neuro-acanthocytosis. So what it is Ö the easiest way to diagnose this particular condition, is to order a peripheral smear. An abnormal acanthal erythrocytes may be seen. There is also degeneration of the posterior columns. I was surprised to hear that in your gastroenterology lecture. But thatís because there is a problem with