Paradoxical subfalcine brain herniation

Case contributed by René Pfleger
Diagnosis certain

Presentation

Patient history temporarily withheld.

Patient Data

Age: 65 years
Gender: Male

3D surface volume rendering 3D VR illustrates marked concavity of the skin in greater parts of right frontal, parietal and temporal surface areas.

Slightly different settings...

ct

Slightly different settings of 3D VR from the same imaging series as before

  • 3D surface rendering from head CT in skin settings depicts subcutaneous line representing ventriculoperitoneal shunt, passing near the coronal suture. Bone settings illustrate status post decompressive hemicraniectomy and parts of the VP shunt along with choroid plexus and pineal gland calcifications i.e. normal intracranial calcifications.
  • Axial brain window slice at the level of septum pellucidum demonstrates marked concavity at the site of decompressive hemicraniectomy. Displacement of the midline structures to the left i.e. subfalcine herniation and associated compressive distortion of the ventricles are also noted.

Axial & coronal MPR from...

ct

Axial & coronal MPR from same imaging series

Demarcated right MCA infarction with loss of substance and secondary dilatation of right lateral ventricle (i.e. chronic phase). Status post right-sided decompressive hemicraniectomy, left-sided VP-shunt with tip in 3rd ventricle near left foramen Monroi. Marked concavity of parts of right hemisphere with slight displacement of the cingulate gyrus beneath the free edge of the falx cerebri without evidence of external mass effect, representing paradoxical subfalcine herniation to the left. Simultaneously slight right-sided transcalvarial herniation of a minor part of right parietal lobe, most likely caused by gravity effects and organized hematoma. 

Conclusion

Head CT obtained in ER 4...

ct

Head CT obtained in ER 4 mth before

Non-contrast CT of the head reveals dense right MCA (M1-3 segments), hypoattenuating brain tissue with sulcal effacement in the territory of the right MCA, obscuration of right lentiform nucleus and loss of right insular ribbon. No significant mass-effect, no hemorrhage. 

Conclusion

Annotated image

In chronological order of the annotated images: 

  1. Dense MCA sign (orange arrows segment M1-2, yellow arrow segment M2-3), loss of insular ribbon sign (blue arrows) compared to contralateral side (normal appearance, green arrow), obscuration of right lentiform nucleus (blue arrow) compared to contralateral side (normal appearance, green arrow) and frontoparietal sulcal effacement, territory of right MCA (white arrows). Note slight mass-effect on right lateral ventricle, cornu frontale et occipitale (dark red arrows).
  2. Demarcating right MCA territory infarct (white arrows) with cytotoxic and vasogenic edema causing subfalcine herniation (yellow arrow) and mass-effect on right lateral ventricle (red arrow).
  3. Two days later at the level of septum pellucidum depicts natural evolution of right MCA infarction with extensive edema and hemorrhagic transformation of different age (red arrows). Resolving subfalcine herniation and interval development of transcalvarial herniation of major parts of the right infarcted hemisphere through newly right-sided frontoparietotemporal hemicraniectomy with scant subcutaneous blood products is also illustrated (yellow arrows). Note demarcating lacunar infarction in left hemithalamus (white arrow), consistent with compression of thalamic perforating arteries from left PCA by brain herniation seen two days before. 
  4. Chronic state of right MCA infarct with resolving edema and petechial hemorrhage, decreased transcalvarial herniation (yellow arrow) and secondary dilatation of right lateral ventricle. Note interval development of lobar hemorrhage (red arrow) in right parietal lobe, most probably due to mass-effect on craniectomy site (parietal bone edge).
  5. Marked concavity of brain and skin flap at the craniectomy site (yellow arrows). Subfalcine herniation to the left (red arrow), compression of both ventricles (purple arrow) and VP-shunt (white arrow) are also noted.
  6. Right frontoparietotemporal cranioplasty flap (blue arrows) with both intra- and extracranial air (white arrows) and moderate amount of blood products both superficially and beneath the flap (red arrows). Note resolved deviation of midline structures.
  7. Two subgaleal organized collections (yellow arrows) consistent with abscesses. Note interval decrease of subdural hematoma without overt cavitation (red arrow).
  8. Note titanium cranioplasty (white arrows) and asymmetry of mesencephalon (yellow arrows) representing right-sided Wallerian degeneration.

Case Discussion

Case key points:

  • the rare and potentially fatal complication of decompressive hemicraniectomy, paradoxical brain herniation, requires early recognition and urgent treatment

  • growing indications for decompressive craniectomy requires the radiologist to be cognizant of the clinical characteristics and imaging appearances of paradoxical brain herniation

  • symptoms and imaging findings that may raise concern/constitute the syndrome are 

    • acute postoperative deterioration after hemicraniectomy with or without temporal association with external ventricular drainage or lumbar puncture

    • sinking skin flap

    • marked concavity at the craniotomy site accompanied by subfalcine and/or transtentorial herniation

What is more, this case illustrates the time course of space-occupying MCA infarction including hemorrhagic transformationWallerian degeneration, decompressive surgery complicated by above mentioned and subgaleal abscess and is a textbook example of the controversy regarding optimal timing of cranioplasty.

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