MRI in Lhermitte-Duclos disease.

Lhermitte-Duclos disease (LDD) is a disorder sometimes referred to as a dysplastic gangliocytoma of the cerebellum. This is a focally indolent growth of the cerebellar cortex in which the folia enlarge due to a profusion of dysplastic cortical neurons and a thickening of the molecular layer. Loss of Purkinje cells and thinning of medullary white matter results. The enlarged folia lose their secondary foldings and asymmetrically expand the cerebellar hemisphere. These morphologic features produce a characteristic pattern on some CTs and all MRIs, affording an opportunity for a preoperative diagnosis. MRI of a pathologic specimen suggested that the abnormal T1 and T2 signals corresponded to the atrophic folial white matter, thickened granule cell layer, and outer molecular layer. Because of inherent Hounsfield artifact in posterior fossa with CT, MRI is the imaging modality of choice, with better visualized striated pattern. The uniqueness of these imaging features obviates the need for an obligatory biopsy for asymptomatic patients and either permits more definitive planning for surgical decompression or, in restricted lesions, guides more assuredly complete excision of the cerebellar mass.

Cauda equina syndrome after in situ arthrodesis for severe spondylolisthesis at the lumbosacral junction.

Relative stretching of the cauda equina over the posterosuperior border of the sacrum can be found in all patients who have Grade-III or IV spondylolisthesis at the lumbosacral junction. We identified twelve patients, all less than eighteen years old, who had cauda equina syndrome after in situ arthrodesis for Grade-III or IV lumbosacral spondylolisthesis. In all twelve patients, posterolateral arthrodesis had been done bilaterally through a midline or paraspinal muscle-splitting approach. Nothing in the operative reports suggested that the cauda equina had been directly injured during any of the procedures. Five of the twelve patients eventually recovered completely. The remaining seven patients had a permanent residual neurological deficit, manifested by complete or partial inability to control the bowel and bladder. If dysfunction of the root of the sacral nerve is noted preoperatively in a patient who has lumbosacral spondylolisthesis, decompression of the cauda equina concomitant with the arthrodesis should be considered. An acute cauda equina syndrome that follows a seemingly uneventful in situ arthrodesis for spondylolisthesis is best treated by an immediate decompression that includes resection of the posterosuperior rim of the dome of the sacrum and the adjacent intervertebral disc. In addition, posterior insertion of instrumentation and reduction of the lumbosacral spondylolisthesis should be considered.