Difficult labour as a cause of communicating syringomyelia.

Although some causes of communicating syringomyelia are known most cases of the disease can only be described as idiopathic. The results of a questionnaire suggest a high incidence of difficult labour in the mothers of syringomyelia patients. A high proportion of patients had forceps deliveries, and a high proportion were the first born in their families. Because the validity of taking a birth history at the age of presentation (mean age 40 y, S.D. 14 for this sample) might be questioned, patients admitted with other disorders (mean age 40 y, S.D. 16) were used as a control group. These patients matched the syringomyelia patients in social class and place of birth. It seems likely that birth trauma may be a cause of tonsillar descent through the foramen magnum (ectopia) and of arachnoiditis; both conditions are often present. Once the tonsils become engaged in the foramen magnum, difference between the cranial and spinal pressure may, over the course of several years, cause the tonsils to descend further, thus leading to communicating syringomyelia. Over half these patients have a history of difficult labour and it is possible that birth injury may be a factor even where birth is regarded as normal.