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I have read with interest the letter recently published on Repeated syncopes and extended paediatric hydrosyringomyelia/Chiari I malformation.1 The case reported is quite unusual, as syncope seems to be a very rare manifestation of this condition, even when associated with a Chiari malformation, at least in adults. From a series of 100 adult patients with syringomyelia diagnosed over the past 10 years at this institute, two thirds of whom had an associated Chiari type I anomaly, only one patient had syncope, which was triggered by sneezing. Another three patients had drop attacks without loss of consciousness, one with a Chiari type I anomaly, and two with an associated ventricular dilatation (figure).
In the paper mentioned by the authors on cardiovascular reflexes in syringomyelia,2 all patients with autonomic involvement, even those without syringobulbia, had an abnormal neurological examination, and sweating abnormalities and Horner’s syndrome were often encountered. The fact that neurological examination was normal in the patient described by Woelfle et al,1 as well as the absence of Horner syndrome and sweating abnormalities, make autonomic dysfunction an unlikely explanation for the episodes described, although it may be a contributing factor. As syncope was associated with occipital headaches, transient brainstem compression may play a significant part. As the authors suggest, the precise mechanism of these episodes and of drop attacks is difficult to determine, and they may be multifactorial.
The authors reply:
As Nogues mentions, the association of hydrosyringomyelia and syncope is a very rare event. To our knowledge, our patient is the first child reported demonstrating such a clinical picture.1-1 In his opinion, the normal neurological examination in our patient makes autonomic dysfunction as the underlying mechanism of the repeated syncopes unlikely. Considering the association of syncope with occipital headache, he suggests that transient brainstem compression may be a causal factor in the mechanism leading to syncope. However, the association of headache was not a consistent finding in all of the five noted syncopal events in our patient. Furthermore, hydrosyringomyelia usually remains asymptomatic in childhood,1-2 indicating a time dependent degree of damage to the spinal cord. Thus, in our opinion a normal neurological status in children does not necessarily exclude temporary dysfunction of the sympathetic system, assuming that temporary, preclinical damage to the spinal cord in childhood may well progress to permanent autonomic dysfunction in adulthood. In addition, even in adults with some symptoms of autonomic dysfunction, the lesion of autonomic outflow paths in the spinal cord may be incomplete, with absence of Horner’s syndrome and preservation of some autonomic reflexes.1-3 In our patient, autonomic dysfunction was supposed to be the most likely mechanism due to the pattern of affected syringomyelic areas in combination with the finding of impaired cardiovascular reflexes in adults with hydrosyringomyelia, in whom longstanding pressure changes may have led to permanent, irreversible destruction of autonomic structures in the medulla.1-4
Of course, we are well aware that all the theoretical models outlined in our case report, even the causal relation between syncope and hydrosyringomyelia/Chiari I malformation, remain speculative and neither his nor our theory can be proved. We agree with Nogues, that probably syncopes and drop attacks in these patients are of multifactorial origin with various possible contributing factors including neurological, cardiovascular, and neuropsychological influences.