Hydromyelia due to Chiari I malformation
Headache worsened with coughing or straining. No neurological deficit in the lower limbs.
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Dysplastic cerebellar tonsils protruding through the foramen magnum with crowding of the cervico-medullary junction especially on the right consistent with Chiari I malformation. Prominent central canal of the cord throughout to the conus with fusiform dilatation in the lower thoracic cord (T6-10)
The herniated cerebellar tonsils are causing relative obstruction to the 4th ventricular outlets (Luschka and Magendie) causing pulsatile CSF to be forced through the obex leading to dilatation of the central canal of the spinal cord with more fusiform dilatation distally (asymptomatic). This is therefore a true hydromyelia as it communicates directly with the central canal both above and below. This is in contrast to a syrinx that is an "outpouching" of the central canal i.e. not ependymal-lined.
Headache with Chiari I malformation linked to coughing is thought to be due to sudden increased intrathecal pressure caused by obstruction to the free flow of CSF in the subarachnoid space.
- Heiss JD, Snyder K, Peterson MM et-al. Pathophysiology of primary spinal syringomyelia. J Neurosurg Spine. 2012;17 (5): 367-80. doi:10.3171/2012.8.SPINE111059 - Free text at pubmed - Pubmed citation
- Sansur CA, Heiss JD, DeVroom HL et-al. Pathophysiology of headache associated with cough in patients with Chiari I malformation. J. Neurosurg. 2003;98 (3): 453-8. doi:10.3171/jns.2003.98.3.0453 - Pubmed citation