Key points Knowledge of anatomy of the meninges is essential for understanding the CT appearances of intracranial bleeding The meninges are thin layers of tissue found between the brain and the inner table of the skull. The meninges comprise the dura mater , the arachnoid , and the pia mater . The dura mater and arachnoid are an anatomical unit, only separated by pathological processes.
The falx cerebri and the tentorium cerebelli are thick infoldings of the meninges which are visible on CT imaging. Elsewhere the meningeal layers are not visible on CT as they are closely applied to the inner table of the skull.
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The meninges Dura mater = tough outermost layer, closely applied to the inner table of the skullArachnoid = thin layer closely applied to the dura materSubarachnoid space = space between the arachnoid mater and the pia mater which contains delicate trabeculated connective tissue and CSFPia mater = very thin layer applied to the surface of the brainThe meninges - clinical significance Knowledge of anatomy of the meninges is essential for understanding the CT appearances of intracranial bleeding Hover on/off image to show/hide findings
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Tentorium cerebelli The tentorium cerebelli - an infolding of the dura mater - forms a tent-like sheet which separates the cerebrum (brain) from the cerebellum The tentorium is anchored by the petrous bones Hover on/off image to show/hide findings
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Tentorium cerebelli On axial slice CT images of the brain the tentorium is faintly visible passing over the cerebellum Tentorium cerebelli - clinical significance In the context of subarachnoid haemorrhage or subdural haematoma the tent may become more dense due to layering of blood Hover on/off image to show/hide findings
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Falx cerebri The falx is an infolding of the meninges which lies in the midline and separates the left and right cerebral hemispheres Falx cerebri - clinical significance Pathological processes may cause 'mass effect' with deviation of the falx towards one side Hover on/off image to show/hide findings
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Falx and tentorium - CT brain/coronal image Coronal slice CT images show that the tentorium cerebelli is continuous with the falx cerebri Falx and tentorium - clinical significance Meningiomas are benign intracranial tumours which may arise from any part of the meninges, including the falx or tentorium 
