During lumbar puncture, which parameter is used to assess intracranial pressure?

• A. Opening pressure
• B. Platelet count
• C. Blood glucose
• D. Serum osmolality

Answer: (A)

Opening pressure is the direct way to gauge intracranial pressure during a lumbar puncture. After you puncture the subarachnoid space, a manometer is connected to the needle and the patient is positioned (commonly in the lateral decubitus or seated position). The height of the CSF column in the manometer reflects the CSF pressure, which in turn mirrors intracranial pressure. An elevated opening pressure points to increased intracranial pressure, as seen in conditions like hydrocephalus or mass effect; a low pressure can suggest CSF hypovolemia or a post‑dural puncture leak. Normal ranges vary by technique and units, but values outside the typical range alert clinicians to abnormal ICP.

Platelet count is checked to reduce bleeding risk with LP, but it does not measure CSF pressure. Blood glucose and serum osmolality relate to systemic metabolism and fluid balance, not to intracranial pressure.