Cerebral Aqueduct/Periaqueductal Lesion



Cerebral Aqueduct/Periaqueductal Lesion


Karen L. Salzman, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Aqueductal Stenosis


  • Tectal Glioma


Less Common



  • Diffuse Axonal Injury (DAI)


  • Neurocysticercosis


  • Multiple Sclerosis


  • Enlarged Perivascular Spaces


  • Diffuse Astrocytoma, Low Grade


  • Encephalitis (Miscellaneous)


  • Intraventricular Hemorrhage


  • Wilson Disease


Rare but Important



  • Metastasis, Parenchymal


  • Wernicke Encephalopathy


  • Behçet Disease


  • Gliomatosis Cerebri (GC)


  • Leigh Syndrome


  • Alexander Disease


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Cerebral aqueduct/periaqueductal lesions may be separated by lesion type



    • Masses & pseudomasses


    • Infectious/inflammatory processes versus metabolic disorders


Helpful Clues for Common Diagnoses



  • Aqueductal Stenosis



    • Focal reduction in aqueduct size, congenital or benign acquired


    • Funnel-shaped aqueduct with “ballooned” lateral & 3rd ventricles & foramen of Monro proximal to obstruction


    • Normal 4th ventricle & foramina distal


    • All patients with suspected AS should be scrutinized for an obstructing mass!


  • Tectal Glioma



    • ↑ T2 signal mass; ± enhancement


    • Expands tectum, obstructs aqueduct


    • Indolent, most only need CSF diversion


Helpful Clues for Less Common Diagnoses



  • Diffuse Axonal Injury (DAI)



    • Multifocal punctate hemorrhages at corticomedullary junction, corpus callosum, deep gray matter (GM) & upper brainstem (dorsolateral midbrain & pons)


    • Multifocal hypointense T2*/GRE foci related to blood product susceptibility


  • Neurocysticercosis



    • Cisterns > parenchyma > ventricles


    • Basal cistern cysts may be racemose (grape-like), causing an aqueduct lesion


  • Multiple Sclerosis



    • Multiple T2 hyperintensities in periventricular white matter (WM) & callososeptal interface; 10% infratentorial


    • Internuclear ophthalmoplegia (INO): Characteristic clinical finding related to brainstem lesion involving medial longitudinal fasciculus, present within periaqueductal region


  • Enlarged Perivascular Spaces



    • Benign fluid-filled structures, accompany penetrating arteries


    • PVS usually 5 mm or less; may expand


    • Most common location for expanded “giant” PVS is midbrain; may cause hydrocephalus


    • Single or multiple well-delineated cysts isointense with CSF; no enhancement


  • Diffuse Astrocytoma, Low Grade



    • Nonenhancing T2 hyperintense mass; supratentorial 2/3, infratentorial 1/3


    • 50% of brainstem “gliomas” are low grade astrocytoma



      • Occur in pons & medulla of children, may involve midbrain


    • Usually no enhancement, if C+ worry about malignant progression


  • Encephalitis (Miscellaneous)



    • Location dependent on etiology


    • Diffuse brain parenchymal inflammation caused by a variety of pathogens, most commonly viruses


    • Abnormal T2 hyperintensity of GM ± WM or deep gray nuclei


    • Epstein-Barr virus: Symmetric BG, thalami, cortex, or brainstem


    • Varicella-zoster virus: Brainstem/cortical GM, cranial nerves


    • Japanese encephalitis: Bilateral thalami, brainstem, cerebellum, spinal cord, cerebral cortex


    • Listeria rhombencephalitis: Brainstem & cerebellum



    • West Nile virus: Brainstem, substantia nigra, BG, thalami, anterior horn (cord), cerebellum


    • Enteroviral encephalomyelitis: Brainstem, spinal cord, & cerebellum


  • Intraventricular Hemorrhage



    • Associated with significant trauma


    • May occur within cerebral aqueduct


  • Wilson Disease



    • Symmetric T2 hyperintensity or mixed signal in putamen, globus pallidus (GP), caudate, & thalami


    • Characteristic “face of the giant panda” sign at midbrain


Helpful Clues for Rare Diagnoses

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on Cerebral Aqueduct/Periaqueductal Lesion

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