Ascending Transtentorial Herniation: A Rare Complication of Posterior Cranial Fossa Tumors and Review of Literature

Abstract

Cerebral herniation is the movement of brain tissue due to increased intracranial pressure. Ascending transtentorial herniation (ATH) is a rare consequence of lesions in the posterior cerebral fossa, often associated with obstructive hydrocephalus. Cerebrospinal fluid (CSF) diversion can alleviate symptoms but may also lead to ATH, particularly after ventriculoperitoneal (VP) shunt procedures. Despite its high mortality, early diagnosis and immediate intervention are crucial. This case report describes a child with a left cerebellar anaplastic ependymoma (CNS WHO grade 3) and obstructive hydrocephalus who developed ATH post-VP shunt and recovered after timely surgical decompression. A 3-year-old boy with a month-long history of headache without associated fever was diagnosed with a cystic lesion in the left cerebellar hemisphere, with obstructive hydrocephalus. Despite an initial plan to avoid CSF diversion, he experienced a hydrocephalic attack, leading to an emergency VP shunt procedure. Postsurgery, he showed signs of ATH and underwent immediate surgical decompression, resulting in a successful recovery and adequate brainstem decompression. In patients with posterior cranial fossa tumors with associated hydrocephalus, it is advisable to do upfront tumor excision and avoid a preoperative CSF diversion procedure. In the rare instance where a patient undergoes CSF diversion procedure before definitive surgery, early detection and immediate intervention are critical for reversing ATH and preserving brain function.

 

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Keywords

ascending transtentorial herniation - hydrocephalus - posterior fossa tumor - ventriculoperitoneal shunt

Introduction

The phrase “cerebral herniation” refers to the movement of a section of the brain from its usual anatomical location to a nearby area.[1] When the intracranial pressure (ICP) rises, pressure gradients form throughout the craniospinal axis, causing brain tissue to herniate.[2] Ascending transtentorial herniation (ATH) is a well-known, although rare, consequence of growing lesions in the posterior cerebral fossa.[3] The tentorium's inner margins separate, forming an oval orifice known as the tentorial incisura. The midbrain is subject to displacement by forces from both below and above the tentorium.[4] Pathogenesis is linked to the formation of a transtentorial pressure gradient ascending from the posterior fossa to the supratentorial compartment.[5] Obstructive hydrocephalus is fairly prevalent, occurring in 71 to 90% of children with posterior fossa tumors.[6] While cerebrospinal fluid (CSF) diversion is necessary for many patients during surgery, preoperative placement of a ventriculoperitoneal (VP) shunt or endoscopic third ventriculostomy (ETV) is generally discouraged, as only 25% of cases ultimately require permanent CSF diversion.[7] [8] CSF diversion may not only alleviate symptoms such as vomiting but also help stabilize intracranial contents, resulting in a free operating field during definitive surgery. However, postoperative deterioration in the patient's state following VP shunt should alert the clinician to the risk of ATH of the brain.[9] [10] ATH is the least understood of the brain herniation syndromes, occurring as a rare consequence of VP shunt with a 3% incidence.[10] We report a case of left cerebellar solid cystic lesion with enhancing mural nodule with obstructive hydrocephalus who developed ATH after VP shunt and recovered after immediate and timely surgical decompression of the posterior cranial fossa.

 

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Case Description

A 3-year-old boy presented with complaints of a 1-month history of headache without associated fever or trauma. On examination, he was alert, playful, and obeying commands. He displayed a tendency of swaying to the left and had dysmetria with cerebellar signs on the left side. His pupils were 3 mm in diameter and reactive to light. Contrast-enhanced magnetic resonance imaging (CEMRI) of the brain revealed a cystic lesion with an enhancing mural nodule in the left cerebellar hemisphere likely with upstream obstructive hydrocephalus ([Fig. 1]). He was initially planned to undergo resection of the tumor without CSF diversion to avoid shunt dependency. However, on day 2 of admission he had a hydrocephalic attack and became unresponsive to pain stimulus with a Glasgow coma scale (GCS) score of E1V1M1; both pupils were 5 mm in diameter and sluggishly reactive to light with bradycardia, hypertension, and irregular breathing (Cushing's triad). He was immediately intubated and put on ventilator. An immediate noncontrast computed tomography (NCCT) of the brain revealed obstructive hydrocephalus with periventricular ooze ([Fig. 2]). He was immediately taken up for right medium-pressure VP shunt (Chhabra SH-202, G. Surgiwear Ltd., India). Clear CSF under high pressure was tapped. Postoperative brain NCCT showed optimal positioning of the shunt ([Fig. 3]). On postoperative day 0, he became alert, oriented, and started following commands. The features of Cushing's triad had resolved. On postoperative day 4, he became drowsy, but was still arousable and obeying commands. He still did not have features of Cushing's triad. Repeat NCCT scan of the brain ([Fig. 4]) showed ATH with rostral displacement of the superior vermis through the tentorial notch, complete obliteration of the quadrigeminal plate cistern, and flattening of the posterior third ventricle along with anterior and superior displacement of the third ventricle. He was immediately taken up for left paramedian suboccipital craniotomy and gross total resection of the lesion via a transcortical approach to decompress the posterior cranial fossa.

Fig. 1 Contrast-enhanced magnetic resonance imaging (CEMRI) of the brain: T2 and T1 contrast sequences of sagittal, coronal, axial sections showing a cystic lesion with enhancing mural nodule in the left cerebellar hemisphere; patent quadrigeminal (A,C; solid arrows) superior cerebellar cisterns (A, B; dashed arrows); and tonsillar herniation (D–F).

Fig. 2 Noncontrast computed tomography (NCCT) of the brain showing obstructive hydrocephalus with periventricular ooze with patent superior cerebellar cistern (dashed arrow) and quadrigeminal cistern (solid arrow).

Fig. 3 Noncontrast computed tomography (NCCT) of the brain on postoperative day 0 of the right ventriculoperitoneal (VP) shunt showing optimal position of the shunt with patent superior cerebellar cistern (dashed arrow) and quadrigeminal cistern (solid arrow) with compression of brainstem against the clivus; the posterior border of the third ventricle is highlighted with a dashed line.

Fig. 4 Noncontrast computed tomography (NCCT) of the brain on postoperative day 6 of ventriculoperitoneal (VP) shunt with ascending transtentorial herniation with complete obliteration of quadrigeminal (solid arrow) and superior cerebellar cistern (dashed arrow) with flattening of the posterior third ventricle (dashed line)—appreciated better by comparing with [Fig. 3].

He was extubated after surgery (on postoperative day 0) and made an uneventful recovery. NCCT of the brain ([Fig. 5]) following definitive surgery showed adequate decompression of the brainstem and patent quadrigeminal and superior cerebellar cisterns. Definitive biopsy revealed the lesion to be anaplastic ependymoma (CNS WHO grade 3). At discharge on day 5 after definitive surgery, he was alert, playful, and moving all four limbs spontaneously. At his last follow-up 3 months after surgery, he was undergoing radiotherapy with the same functional status.

Fig. 5 Noncontrast computed tomography (NCCT) of the brain following left paraforaminal paramedian suboccipital craniotomy and resection of tumor with resolution of ascending transtentorial herniation (ATH) with patent quadrigeminal (solid arrow) and superior cerebellar cisterns (dashed arrow).

 

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Discussion

Meyer described ATH for the first time in 1920, reporting an uncommon supratentorial distention of the splenium.[11] [12] In 1938, LeBeau described displacement of the cerebellar dome up through the tentorial gap in a rare instance of cerebellar tumor.[13] The lateral ventriculogram revealed an apparent ablation of the posterior part of the third ventricle. Vastine and Kinney discovered that the pineal body shifted upward in 33% of the patients with subtentorial gliomas. Before the pineal gland is elevated, there must be a significant upward shift in the midbrain.[4] Johnson and List mentioned that uncommon, large tumors of the pons may move the brainstem anteriorly, causing a corresponding elevation of the third ventricle.[13] In 1979, Cuneo et al described this phenomenon as “the least understood of the brain herniation syndromes.”[4]

The type of herniation that occurs is influenced by the width of the tentorial notch and the direction of the mass effect (whether it is upward or downward). ATH is more likely to happen in individuals with a broad tentorial notch and an upward mass effect.[1] A cerebellar lesion is the most common cause of ATH (65%), followed by cerebellopontine angle, pons, and fourth ventricle lesions.[12] It is likely that posterior fossa lesions sufficiently large to cause considerable upward displacement also block CSF pathways. By establishing an equilibrium of forces, the ensuing hydrocephalus may prevent upward herniation.[14] Displacement of the cerebellum into the tentorial incisura is more likely to occur when the mass originates near the incisura, for example, in the cerebellar vermis, when drainage of the lateral ventricles relieves obstructive hydrocephalus and reduces pressure above, and when the opening in the tentorium is wide.[4] The brainstem is initially squeezed against the clivus. As the process of enlargement progresses, tonsillar herniation into the foramen magnum occurs, blocking the inferior outflow of the posterior fossa and squeezing the medulla. When this is not lethal, growing pressure in the posterior fossa will result in upward displacement through the tentorial notch.[3] The protruding tissue endangers both the great vein of Galen and the superior cerebellar arteries, pushing the midbrain forward and eventually compressing it from behind.[15] Cranial CT can precisely detect the rostral displacement of the superior vermis through the tentorial notch. Early or impending upward herniation is indicated by compression and slight posterior flattening of the quadrigeminal plate cistern. As herniation worsens, it results in amputation of the peritectal CSF diamond, giving the confluent quadrigeminal and superior cerebellar cisterns a triangular or “squared-off” appearance. In severe cases, the herniated vermis fills the notch, completely eliminating these cisterns and flattening the posterior third ventricle.[16]

The primary symptom of acute ATH herniation is a gradual decline in consciousness,[4] [9] [12] [17] [18] caused by impaired function of the reticular formation at the mesencephalopontine junction.[17] It is well understood that midbrain ascending reticular activating circuits play an important role in maintaining consciousness. In this regard, compression of the midbrain with a related compromise of its blood supply may be a factor in inducing and maintaining a state of unconsciousness that emerges and worsens as this complication develops.[15] [19] Components of Cushing's triad such as bradycardia and hypertension, and irregular respiration, have been reported in other cases of ATH, particularly those involving acute deterioration following sudden CSF drainage.[2] [10] [12] [20] [21] [22] However, many authors perform direct tumor removal with an intraoperative external ventricular drain (EVD) if needed for patients of posterior fossa tumor with hydrocephalus. This avoids the need for a VP shunt and also avoids the dreaded ATH.

Primary surgical excision of the tumor is strongly considered the preferred initial strategy to directly address the mass effect and avoid ATH.[20] Patients with midline posterior fossa tumors may be considered for corrective surgery of the lesion first, rather than palliative procedures like shunt surgery or ETV, as these procedures have the potential to precipitate reverse herniation of the brain.[20] Since only 25% of patients need permanent CSF diversion, therapy with a ventriculoperitoneal shunt or ETV before tumor excision is not advised, even if many patients need it at the time of surgery.[7] [8] If immediate excision is not feasible, controlled CSF drainage may be considered.[23] However, this strategy carries a significant risk of ATH, also known as reverse brain herniation (RBH).[1] [6] [24] RBH/ATH is rare,[6] [10] [23] with incidence reported around 3%,[6] [10] [23] but it is associated with a significant high mortality.[6] [10] [23] [24] ATH is caused by a sudden decrease in supratentorial pressure,[5] [6] [9] [10] [12] [20] [22] reversing the pressure gradient across the tentorium.[5] [12] [20] [22] This sudden decompression, often following a shunt surgery or ETV, in the presence of a space-occupying lesion in the posterior fossa, may cause upward herniation.[20] Allowing a liberal amount of CSF to leak during surgery or using low-pressure VP shunt tubes may lead to reverse coning.[24] In such cases, it is crucial to slowly and carefully reduce the ventricular pressure. Programmable shunt or even an EVD may be better alternatives in such cases as the CSF output can be carefully monitored and controlled.[23] Throughout this process, one should closely monitor cardiovascular function and heart rhythm for any changes. If arrhythmias are detected, it is advisable to immediately halt the drainage of CSF. In case there is significant hemodynamic disturbances, one should reinject the drained CSF or normal saline into the ventricular catheter.[2] Vigilance for ATH and prompt intervention are paramount regardless of the initial approach.[10] [23] [24] Early detection and immediate intervention are crucial for reversing ATH and preserving brain function. Surgical decompression should be undertaken as soon as possible, even in cases of severe RBH.[6] [10]

In the series by Cuneo et al, only 7 cases out of a total of 52 reviewed were diagnosed antemortem and the mortality was 100%.[4] [6] To our knowledge, four such cases have been reported in the literature recently ([Table 1]). More recent cases documented in the literature showed improved outcomes.[2] [6] [10] We believe that this condition is highly underdiagnosed because a delay in diagnosis can prove to be fatal and not give time for imaging studies and further action. Despite the high mortality associated with ATH, it is essential to perform surgical decompression as soon as possible, even in severe cases. Ventricular drainage directly causes herniation in approximately 25% of patients. Therefore, patients who undergo CSF diversion must be closely monitored for ATH after the procedure.[6] In our case, the patient made an uneventful recovery following urgent and timely decompression of the posterior cranial fossa. In hindsight, upfront tumor excision should have been performed early. Additionally, when the patient deteriorated on the second day following admission, inserting an EVD or placing a programmable VP shunt could have been better as these options would have allowed for controlled CSF drainage.

Table 1 Case reports of ATH following CSF diversion in patients with posterior cranial fossa tumors[6]

Sl. no.	Study	Age/gender	Diagnosis	Treatment	Outcome
1	Singha et al[20]	57 y/M	Midline posterior fossa (involving vermis and both cerebellums) hemangioblastoma with hydrocephalus	ETV + suboccipital craniectomy and tumor decompression	Uneventful
2	Gurajala et al[10]	45 y/M	Right cerebellopontine (CP) angle tumors with hydrocephalus	VP shunt + tumor decompression	Discharged with nasogastric tube
3	Marappan et al[24]	3.5 y/F	Fourth intraventricular tumor	VP shunt	Not available
4	Tyngkan et al[6]	12 y/F	Left cerebellar lesion	VP shunt	Deceased
5	Present case	3 y/M	Left cerebellar anaplastic ependymoma	VP shunt followed by tumor excision	Discharged in good condition

Abbreviations: ATH, ascending transtentorial herniation; CSF, cerebrospinal fluid; ETV, endoscopic third ventriculostomy; VP, ventriculoperitoneal.

 

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Conclusion

Primary surgical excision of posterior fossa tumors is strongly considered the preferred initial management strategy in patients with obstructive hydrocephalus. This directly addresses the mass effect and aims to mitigate the significant risk of ATH, a serious complication associated with CSF diversion procedures (VP shunt, EVD, ETV) due to sudden pressure changes. Controlled CSF drainage might be considered if primary excision is not feasible or hydrocephalus persists. Vigilance for ATH and prompt intervention are paramount. Early signs of this condition must be promptly identified, and swift action should be taken to reverse the process and preserve brain function.

 

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Conflict of Interest

None declared.

• References

• 1 Gürsoy M, Çallı C. Herniation Syndromes. In book: Emergency Radiology of the Head and Spine. Cham: Springer; 2022: 235-244
• 2 Prabhakar H, Umesh G, Chouhan RS, Bithal PK. Reverse brain herniation during posterior fossa surgery. J Neurosurg Anesthesiol 2003; 15 (03) 267-269
• 3 Spiegelmann R, Hadani M, Ram Z, Faibel M, Shacked I. Upward transtentorial herniation: a complication of postoperative edema at the cervicomedullary junction. Neurosurgery 1989; 24 (02) 284-288
• 4 Cuneo RA, Caronna JJ, Pitts L, Townsend J, Winestock DP. Upward transtentorial herniation: seven cases and a literature review. Arch Neurol 1979; 36 (10) 618-623
• 5 Manohar N, Varadharajan S, Ramesh VJ, Chakrabarti D. Reverse herniation-forethought before EVD placement. J Neurosurg Anesthesiol 2017; 29 (03) 366-367
• 6 Tyngkan L, Singh A, Singh M, Bhat AR. A reverse brain herniation (RBH) after ventriculoperitoneal shunt (VP) in posterior fossa tumour with obstructive hydrocephalus. Rom Neurosurg 2021; 35 (03) 352-354
• 7 Schneider C, Ramaswamy V, Kulkarni AV. et al. Clinical implications of medulloblastoma subgroups: incidence of CSF diversion surgery. J Neurosurg Pediatr 2015; 15 (03) 236-242
• 8 Santos de Oliveira R, Barros Jucá CE, Valera ET. et al. Hydrocephalus in posterior fossa tumors in children. Are there factors that determine a need for permanent cerebrospinal fluid diversion? | Child's Nervous System. Accessed May 23, 2025 at: https://link.springer.com/article/10.1007/s00381-008-0649-x
• 9 Yadav G, Sisodia R, Khuba S, Mishra L. Anesthetic management of a case of transtentorial upward herniation: an uncommon emergency situation. J Anaesthesiol Clin Pharmacol 2012; 28 (03) 413-415
• 10 Gurajala I, Brahmaprasad V, Rajesh A, Ramachandran G, Purohit AK. Reverse brain herniation following ventriculoperitoneal shunt. Indian J Anaesth 2012; 56 (06) 585-587
• 11 Meyer A. Herniation of the brain. J Nerv Ment Dis 1920; 4 (04) 387-400
• 12 Moscardini-Martelli J, Ponce-Gomez JA, Alcocer-Barradas V. et al. Upward transtentorial herniation: a new role for endoscopic third ventriculostomy. Surg Neurol Int 2021; 12: 334
• 13 Ecker A. Upward transtentorial herniation of the brain stem and cerebellum due to tumor of the posterior fossa with special note on tumors of the acoustic nerve. J Neurosurg 1948; 5 (01) 51-61
• 14 Eisenberg HM, Sarwar M. Ventriculographic features of ascending transtentorial herniation. Acta Neurochir (Wien) 1978; 42 (3–4): 225-228
• 15 Sunderland S. The tentorial notch and complications produced by herniations of the brain through that aperture. Br J Surg 1958; 45 (193) 422-438
• 16 Osborn AG, Heaston DK, Wing SD. Diagnosis of ascending transtentorial herniation by cranial computed tomography. AJR Am J Roentgenol 1978; 130 (04) 755-760
• 17 Knüpling R, Fuchs EC, Stoltenburg G, Gerull G, Giesen M, Mrowinski D. Chronic and acute transtentorial herniation with tumours of the posterior cranial fossa. Neurochirurgia (Stuttg) 1979; 22 (01) 9-17
• 18 Adamson DC, Dimitrov DF, Bronec PR. Upward transtentorial herniation, hydrocephalus, and cerebellar edema in hypertensive encephalopathy. Neurologist 2005; 11 (03) 171-175
• 19 LRCH. Brain mechanisms and consciousness. Postgrad Med J 1955; 31 (353) 141
• 20 Singha SK, Chatterjee N, Neema PK. Reverse herniation of brain: a less recognized complication in a patient with midline posterior fossa tumor postendoscopic third ventriculostomy. J Neurosurg Anesthesiol 2009; 21 (04) 354-355
• 21 Woo PYM, Lo WHY, Wong HT, Chan KY. The “negative” impact of a subgaleal drain: post-cranioplasty negative pressure subgaleal drain-induced ascending transtentorial herniation. Asian J Neurosurg 2019; 14 (01) 256-261
• 22 Mehta V, Bakhsheshian J, Dorafshar AH, Ahn ES. Upward transtentorial herniation following frontoorbital advancement for syndromic craniosynostosis: case report. Neurosurg Focus 2015; 38 (05) E8
• 23 Singla N, Kapoor A, Chatterjee D. Diagnosing early upward cerebellar herniation by computed tomography: a diagnostic boom, a savior. Surg Neurol Int 2016; 7 (01) 72-72
• 24 Marappan K, Sankaran A, Deiveegan K, Ross K. A Known complication of posterior fossa tumor rarely encountered-reverse coning. Apollo Med 2018; 15 (04) 183

Publication History

Article published online:
28 August 2025