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We read with interest the article by Paulig and Prosiegel1 concerning a patient initially diagnosed with amyotrophic lateral sclerosis (ALS), who had suffered from progressive swallowing difficulties, fibrillations, and tongue atrophy for a year, in the context of a flaccid bulbar palsy. Brain and spinal MRI showed a Chiari I malformation with descent of the cerebellar tonsils. The authors accompany their article with an illustration of the patient, showing extensive bilateral paresis and atrophy of the tongue. The article notes the importance of carrying out an MRI examination on those patients who show bulbar palsy mimicking bulbar onset type ALS in order to rule out Chiari I malformation.
Chiari I malformation has also recently been reported as being associated with bulbar onset ALS.2 Nevertheless, the marked improvement in the dysphagia after neurosurgery suggests that Chiari I was the cause of the patient’s bulbar palsy.
Dysphagia with predominant signs of lower motor neurone disease as the sole manifestation of adult Chiari I malformation is unusual.3 Pressure exerted by the cerebellar tonsils on the hypoglossal nuclei and other swallowing centres located in the medulla is hypothesised by the authors to be a main cause of the dysphagia.
The importance of the reported case was the appearance of tongue atrophy over a relatively short period of time. In the three patients with dysphagia as the sole manifestation of Chiari I reported to date, the complaint had been present for at least three and a half years and none of the patients had tongue atrophy.4–6
We would like to comment on the importance of asymmetry of the face and mouth. A detailed examination of the picture1 shows deviation of the mandible to the right, suggesting that there was at least trigeminal nerve motor involvement. Another important clinical detail that was not mentioned is whether the patient had speech abnormalities. The muscles used in speech are basically the same as those used in swallowing (innervated by the hypoglossal, vagal, glossopharyngeal, facial, and trigeminal motor cranial nerves).7
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Author’s reply
We would like to thank Dr Gamez et al for their interest in our case report and their helpful comments on it.
They emphasise the appearance of the tongue atrophy in our patient, which had developed over a short period of time and was not present in three other case reports where dysphagia was the sole manifestation of a Chiari I malformation. Indeed, in those patients signs of lower motor neurone damage were not reported. Obviously, dysphagia as a manifestation of a Chiari malformation can develop from different mechanisms—“central” damage to the medullary pattern generators for swallowing and/or to the (supranuclear) descending corticobulbar pathways in the lower brain stem (that is, dysphagia without tongue atrophy); and “peripheral” damage to the motor neurones of the hypoglossal nerves sited in the dorsal medulla oblongata, possibly accompanied by central damage mentioned above (that is, dysphagia with tongue atrophy).
In our paper our main aim was to emphasise the second mechanism, which clinically mimics a bulbar onset of ALS and may lead to a wrong diagnosis. The period of one year after the first onset of dysphagic symptoms may appear relatively short with regard to the marked tongue atrophy. However, it is very likely that the chronic process of pressure in the Chiari malformation triggers neuronal destruction in the hypoglossal nuclei preceding the clinical manifestation of dysphagia due to compensation of incomplete axonal loss.
With regard to asymmetry of the face, which was very well identified in our picture by Gamez and his colleagues, there were no clinical signs suggesting involvement of the trigeminal motor nucleus. The latter is situated in the mid portion of the pons, and pressure exerted on pontine structures would have been expected to cause other signs of involvement of this part of the brain stem, but this was not the case. We would prefer an alternative explanation—that is that the patient had difficulty in protruding her tongue, which was asymmetrically impaired (right more than left, as can be seen in the picture) and she tried to overcome this by (unconscious) asymmetrical coactivation of the jaw muscles.
Concerning the question of speech abnormalities raised by Dr Gamez, our patient did indeed have slightly slurred speech, another symptom that may be misinterpreted as a sign of ALS.