Idiopathic Intracranial Hypertension (IIH): This condition is characterized by elevated intracranial pressure without a detectable cause, often presenting with symptoms such as headache, vision changes, and papilledema. It is the most likely diagnosis given the presentation of increased intracranial pressure without an identifiable secondary cause.

Cerebral Venous Sinus Thrombosis: A condition where a blood clot forms in the brain's venous sinuses, which can mimic IIH by causing increased intracranial pressure. Symptoms can include headache, vision problems, and seizures.
Space-Occupying Lesions: Tumors or cysts that take up space within the skull, potentially increasing intracranial pressure. These could include meningiomas, acoustic neuromas, or arachnoid cysts.
Hydrocephalus: A condition where there is an accumulation of cerebrospinal fluid (CSF) within the brain, leading to increased pressure. This can be due to various causes, including obstruction of CSF pathways or impaired CSF absorption.

Meningitis: Inflammation of the protective membranes covering the brain and spinal cord, which can be life-threatening if not promptly treated. Symptoms include severe headache, fever, and stiff neck.
Subarachnoid Hemorrhage: Bleeding into the space between the brain and the tissue that covers it, often due to an aneurysm rupture. This is a medical emergency with symptoms including sudden severe headache, vomiting, and loss of consciousness.
Pituitary Apoplexy: A condition where there is sudden hemorrhage or infarction of the pituitary gland, leading to acute increase in intracranial pressure. Symptoms can include severe headache, visual disturbances, and acute hormonal deficiencies.

Pseudotumor Cerebri Syndrome due to Medications: Certain medications, such as tetracyclines, vitamin A derivatives, and growth hormone, can cause increased intracranial pressure as a side effect.
Sarcoidosis: A systemic disease that can affect the central nervous system, leading to increased intracranial pressure among other neurological manifestations.
Neurosarcoidosis: Direct involvement of the nervous system by sarcoidosis, which can cause a variety of neurological symptoms including increased intracranial pressure.