Spontaneous ligamentum flavum hematoma in the lumbar spine.

Lumbar or sacral nerve root compression is most commonly caused by intervertebral disc degeneration and/or herniation. Less frequently, other extradural causes may be implicated, such as infection, neoplasm, epidural hematoma, or ligamentum flavum pathology. We present the case of a patient with spontaneous ligamentum flavum hematoma compressing the L4 nerve root, without antecedent trauma. Although exceedingly rare, the diagnosis of ligamentum flavum pathology in general, and that of ligamentum flavum hematoma in particular, should be considered on those rare occasions when the etiology of lumbar or sacral nerve root compressions appears enigmatic on radiological studies. Usually surgical treatment produces excellent clinical outcome.