Idiopathic transdural spinal cord herniation: report of two cases and literature review.

BACKGROUND: Idiopathic transdural spinal cord herniation (ISCH) is a rare entity with postsurgical and post-trauma forms. ISCH is often omited in the preoperative evaluation. It often affects the thoracic segment and presents clinically as a rare cause of progressive myelopathy or Brown-Séquard syndrome, whose diagnosis is established by magnetic resonance imaging (MRI). We report on this rare entity due to its difficult diagnosis, making optimal management difficult. CLINICAL CASE: We present the cases of two patients with ISCH who were misdiagnosed and operated on in other spinal segments without reaching an accurate diagnosis. In our institution, patients with clinical suspicion were evaluated by imaging studies in order to rule out other pathologies. Laminectomy was performed on the involved levels, reducing herniation and with the placement of a synthetic spinal patch to the duramater. CONCLUSIONS: ISCH has been attributed to congenital weakness of the duramater or the dural ventral duplication with herniation through the inner layer due to continuous pressure from cerebrospinal fluid that pushes the marrow out of the subdural space. It is estimated that presurgical diagnosis is done only in one third of the cases, confirmed by MRI. Surgery is performed on patients with symptom progression. Surveillance in those patients with mild symptoms is recommended. Treatment may allow recovery of the neurological deficit, improving motor affection in 80% of patients and sensory affection in 35%.