Friday 5 August 2011

Post lumbar puncture intracranial hypotension

A 30 yo male patient with headache since 2 days.
MRI brain: axial T2 images and  midline sagittal T1 image, MR Venogram.
Important findings:
1. Generalized effacement of hemispheric cortical sulci. Mild compression over lateral ventricles.
2. Dural venous sinuses bulky and round on cross section (normally dural venous sinus has triangular shape on cross sections), but show normal T2 flow voids and normal flow related signals on MR Venogram.
4. Sagittal T1 image show slightly low lying cerebellar tonsils.
After seeing MRI, when leading questions asked to patient's relative about any previous consultations, revealed history of a single day IPD admission 3 days back in some other hospital with lumbar puncture.  
So it’s a case of post lumbar puncture intracranial hypotension presenting with headache and is common.
Patient given head low and improved.

Intracranial hypotension

Syndrome of headache caused by reduced intracranial CSF pressure.

Imaging wise diagnostic clue is its classical triad.  
1 Brain stem sagging.
2 Dilatation of veins and dural sinuses.
3 Dural thickening with enhancement, subdural fluid collections.
....not expected in every case, absence of any one of them does not preclude the diagnosis.

CT; relatively insensitive; may appear normal. May show subdural fluid collections, is often bilateral. Obliterated Suprasellar cisterns. Compressed lateral ventricles.
MRI is the investigation of choice due to its multi planner capability provides sagittal as well as coronal sections. As it provides sagittal sections which may show other associated findings like Optic chiasm, hypothalamus draped over sella, caudal displacement of cerebellar tonsils. MRI provides better characterization of sub dural fluid collection whether its sub dural effusion or hematoma. If its hematoma signals of collection will vary depending up on the age of hematoma on various sequences. MR is more sensitive to dural thickening and enhancement than CT.

Chronic SDH : Membrane formation in the hematoma, enhancing membranes enclosing blood products may be seen. No "sagging midbrain"
Dural sinus thrombosis with venous engorgement
Post surgical dural thickening.
Idiopathic hypertrophic cranial pachymeningitis.

Clinical Presentation: 
Most common sign /symptom is severe headache can be orthostatic, persistent, pulsatile or even associated with nuchal rigidity.
CN palsy often abducens, visual disturbances are uncommon.
Severe encephalopathy with disturbances of consciousness is rare.

Aimed at restoring CSF volume by fluid replacement.
Bed res with head low.
Active leak, Lumbar or directed epidural blood patch.Intrathecal saline infusion.
If blood patch fails dural suturing, packing with muscle pledget, Gelfoam or fribrin glue. 

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