Pseudoarachnoiditis in Spontaneous Intracranial Hypotension

The most common causes of intracranial hypotension include persistent cerebrospinal fluid (CSF) leakage from lumbar puncture, spontaneous CSF leakage, or excessive CSF drainage. Spontaneous intracranial hypotension (SIH) is defined as a syndrome of reduced CSF pressure that occurs in the absence of dural puncture, surgery, or trauma. The pathogenesis is generally thought to be an occult leak of CSF through small defects in the meninges, with a resultant decrease in CSF volume and pressure (1). Intracranial hypotension typically presents with postural headaches. Typical findings on brain magnetic resonance imaging (MRI) are diffuse pachymeningeal enhancement, subdural fluid collections, pituitary hyperemia, engorgement of venous structures, and brain sagging, although brain MRI scans are sometimes normal (1). Spinal imaging is usually recommended if brain MRI yields normal findings or if treatments fail. Although numerous spinal MRI findings of SIH have been described (2), we report a novel case of SIH in which the brain MRI scan was normal, but the lumbar spinal MRI revealed clustering of the cauda equina fibers mimicking arachnoiditis.