IN THEIR ARTICLE on papilledema and obstructive sleep apnea syndrome, Purvin et al1 illustrated another important finding to add to the cluster of symptoms known as "pseudotumor cerebri." When this condition was first described by Quincke2 in 1897, pseudotumor cerebri (named in 1904 by Nönne3) was a condition of unknown cause with clinical findings including papilledema, normal spinal fluid contents, and high spinal fluid pressure. Subsequently, arteriography and pneumoencephalography were developed, and these procedures were performed to rule out tumor and hydrocephalus. While it was known that venous sinus occlusion also could cause increased intracranial pressure with normal spinal fluid contents, angiography was performed to look only at the arterial elements and for evidence of tumor within the intracranial space, not to examine the venous sinuses. Since the middle 1970s, computed tomography, magnetic resonance imaging, and magnetic resonance venography have been used to exclude tumor, hydrocephalus, and venous sinus occlusion as potential causes of increased intracranial pressure. Several terms have been proposed to encompass the symptoms and clinical findings of this condition, including pseudoabscess, serous meningitis, otitic hydrocephalus, toxic hydrocephalus, and benign intracranial hypertension, as well as pseudotumor cerebri. However, none of these names is particularly useful since the condition is not due to an infection, is not inflammatory in nature, is rarely due to ear disease (with venous sinus occlusion), is occasionally caused by toxins, and is not visually benign. Since the condition was first diagnosed, several unequivocal causes of pseudotumor cerebri have emerged. Both intracranial venous sinus occlusion and extracranial venous sinus occlusion can cause increased intracranial pressure. Vitamin A toxicity, including that occurring from 13-cis-retinoic acid, the various retinoids used to treat malignant neoplasms, and ingestion of the livers of polar bear, calves, fish, shark, and chicken, which store large amounts of vitamin A, all have the potential for causing increased intracranial pressure. Brain growth disproportionate to skull growth in children who are treated for deprivation dwarfism and childhood myxedema, as well as the various craniosynostoses and the use of growth hormone, have all been accompanied by elevated intracranial pressure, normal spinal fluid contents, and papilledema. Each of these conditions and many more dubious, unproven causal relationships have been reported as "pseudotumor cerebri caused by _________."