In a patient with raised intracranial pressure, cerebrospinal fluid can drain through which route to the lymphatics of the nasal mucosa — accounting for up to 50% of CSF absorption in some studies?

• A Through the arachnoid granulations (Pacchionian bodies) into the superior sagittal sinus only
• B Through the cribriform plate of the ethmoid bone along the sheaths of the olfactory nerve filaments into the nasal submucosa lymphatics ✓
• C Through the choroid plexus by reverse flow
• D Through the foramen magnum into the cervical subarachnoid space and then spinal epidural veins

Explanation

While the arachnoid granulations draining into the dural venous sinuses (predominantly SSS) are the classic and primary route for CSF absorption, an important alternative pathway is across the cribriform plate of the ethmoid bone. CSF flows along the perineural spaces of the olfactory nerve filaments as they pass through the cribriform foramina into the submucosa of the olfactory region of the nasal cavity, where it is absorbed by nasal lymphatics draining to cervical lymph nodes. This route gains clinical importance in post-traumatic anosmia (CSF rhinorrhoea from cribriform plate fractures), where it may cause meningitis, and may also explain olfactory changes in normal-pressure hydrocephalus.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.