Childs Nerv Syst DOI 10.1007/s00381-009-1027-z
CASE REPORT
Chronic uncal herniation secondary to posterior fossa shunting: case report and literature review Suhas Udayakumaran & Liat Ben Sira & Shlomi Constantini
Received: 7 October 2009 # Springer-Verlag 2009
Abstract Introduction Chronic herniation syndromes other than tonsillar herniation are not well-recognized. Transtentorial uncal herniation in its chronic form has been reported in only few case reports (Horowitz et al., J Neuroimaging 12:78–79, 2002; Naidich et al., Radiology 158:431–434, 1986; Ng and Valiante, J Clin Neurosci 16:944, 2009; Ng and Valiante, J Clin Neurosci 16:984, 2009). We hereby illustrate a case with this rare finding, including MR imaging, and analyze this phenomenon. Case report A 15-year-old girl had a resection of a cerebellar pilocytic astrocytoma at 5 years of age. Two months later, she underwent a cystoperitoneal shunt for persistent headache and pseudomeningocele, secondary to an enlarging cyst at the tumor bed. Subsequently, her shunt was upgraded to a more conservative valve following clinical evidence of over drainage. This was also associated with imaging compatible with bilateral uncal herniation. After the procedure, she had relief of symptoms. Conclusion We conclude that a negative pressure gradient in the posterior fossa, relative to the supratentorial compartment, is the etiology of the chronic uncal hernia-
S. Udayakumaran : S. Constantini (*) Department of Paediatric Neurosurgery, Dana Children’s Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv University, 6 Weizman St., Tel Aviv 64239, Israel e-mail:
[email protected] L. Ben Sira Paediatric Radiology, Dana Children’s Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv University, 6 Weizman St., Tel Aviv 64239, Israel
tion in our patient. Comparing the case reports in the literature with our case, we postulate that chronic uncal herniation is a complication of shunting of a posterior fossa fluid cavity in children, many of them with Dandy–Walker syndrome and/or other cerebellar cystic formations. The treatment priority at presentation should be to rule out shunt malfunction. In the event of association with clinical over-drainage syndrome, there may be a role for changing the shunt system into a more conservative drainage combination. Keywords Chronic uncal herniation . Tentorial herniation . Herniation syndromes . Intracranial hypotension . Posterior fossa shunt . Dandy–Walker syndrome . Cystoperitoneal shunt
Introduction Various cerebral herniation syndromes are well-known. Transtentorial herniation in its acute form is a wellrecognized entity with dismal clinical implications. It is usually related to a supratentorial downward driving force and raised intracranial pressure (ICP). It may also be related transiently to postcraniotomy hypovolemia [6]. Chronic herniation syndromes, other than tonsillar herniation in Chiari malformation, are not well-recognized. Transtentorial herniation in its chronic form has been reported only in a few case reports, with undefined pathophysiology and clinical implications [5, 8, 12, 13]. We hereby present a case of chronic uncal herniation where the pathophysiology seems clear. Implications for surgical treatment will be discussed.
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Fig. 1 Cranial CT demonstrating postoperative changes including the collapsed peritumoral cyst in the right cerebellar hemisphere (arrow) with a shunt catheter tip seen within the cavity
proximal disconnection and the second a documented distal malfunction. In the last 2 years, she continues to present to us with intermittent, transient symptoms of diplopia and headache. Cranial computer tomography (CT) during these episodes has revealed no evidence suggestive of shunt malfunction. The ventricles remain undilated and show the posterior fossa shunt with a collapsed cyst (Fig. 1). Repeated fundoscopy during these episodes showed no papilloedema. According to the patient, these episodes would disappear with analgesics and by resting in a horizontal position. A recent MR showed persistent bilateral uncal herniation. This was associated with undilated ventricles (Fig. 2). The posterior fossa appeared “tight” with a slit-like fourth ventricle and cystic cavity. It also showed venous engorgement associated dural enhancement of posterior fossa meninges (Fig. 3). In view of her transient symptomatology and doubtful clinical significance of the imaging finding, we are closely following her and may intervene depending on her progress.
Case report
Discussion
A 15-year-old girl had a resection of cerebellar cystic pilocytic astrocytoma at 5 years of age. Postoperatively, she developed symptoms secondary to an enlarging cyst at the tumor bed. Two months later, she underwent a cystoperitoneal shunt (CPS), with a low-pressure valve, for persistent headache and pseudomeningocele. Subsequently, 8 months later, her shunt was upgraded for symptoms of headache associated with radiological evidence of over drainage and bilateral uncal herniation. She had relief of her symptoms. At the age of 11 and 13 years, she had shunt revisions for suspected shunt malfunction; one was an episode of
The earliest clear description of uncal herniation per se is attributed to Adolf Meyer (1866-1950), who, in 1920, described a supratentorial tumor causing tentorial herniation, which impinged on the posterior cerebral artery and caused hemianopia. He reported: “The falx and tentorium constitute an important protection against any sudden impacts of pressure by keeping apart heavy portions of the brain, but they also provide an opportunity for trouble in case of swelling or need of displacement” [1]. Transtentorial herniation in its acute form is well-recognized and is usually related to a supratentorial driving force and raised ICP. It may also be related transiently to postcraniotomy
Fig. 2 A recent MR axial T2 and coronal T1-weighted images, showing bilateral parahippocampal herniation (arrows). The ventricles are nondilated
Childs Nerv Syst Fig. 3 Recent sagittal T1and axial postgadolinium demonstrating herniation of left cerebellar tonsil (arrow) with prominent dural venous engorgement, “slit like” fourth ventricle and tight posterior fossa
hypovolemia [6]. Lumbar puncture in a patient with unilateral high ICP may precipitate uncal herniation and lead to a full-blown brainstem compression syndrome. Transtentorial herniation in its chronic form has been reported in a few case reports with somewhat confusing clinical implications and unclear pathophysiology. To the best of our knowledge, three other publications are available, with a total of ten patients (including our patient), in the English literature on this issue [5, 8, 12, 13]. Most of these reported cases were in the pre-MR era. Table 1 represents a summary of the published case reports. A combined meta-analysis of all the described patients with this phenomenon highlights the following features: &
Age: The age of presentation is usually pediatric (eight of ten patients). Two patients in the series were adults. One of the adult patient aged 27 had his first clinical presentation at 12 years of age. Early age of presenta-
&
tion may be related to the underlying condition that led to shunting of the posterior fossa [Dandy–Walker syndrome (DWS) and cerebellar cystic lesion] or to increased deformability of brain tissue in children. Nine of ten patients had posterior fossa CPS, and eight patients had DWS. Our patient had a cerebellar cyst secondary to total removal of cerebellar astrocytoma. It seems obvious from these facts that this complication is specific to the presence of a draining shunt in the posterior fossa.
The explained pathophysiology seems to be quite trivial in these cases. The continuous drainage of cerebrospinal fluid induced by the posterior fossa shunt results in a chronic negative pressure gradient between the supra- and infratentorial compartments. This negative pressure creates a vector of force, leading to downward displacement of the
Table 1 Summary of published case reports Patient series
Age at presentation
Type of shunt (CP/VP/Both)
Basic clinical diagnosis
Symptomatology
Ng et al. [12, 13], n=1 (2009)
27 years
CP
Dandy–Walker syndrome
Naidich et al. [8], n=7 (1986)
Less than 13 (2 infants)
3 CP 4 CP+VP
Dandy–Walker syndrome
Complex partial Resection of the seizure (since herniated portion 15 years of age) 4 shunt malfunction 4 patients multiple shunt revision 1 EVD in posterior 2 died fossa shunt 2 unknown Headache Shunt upgrade and Vomiting observation Diplopia Neuralgia Biopsy of the herniated portion
Our patient
12 years
CP
Cerebellar cystic astrocytoma
Horowitz M et al. [5], n=1 (2002)
41 years
No shunt
Atypical trigeminal neuralgia
Management
Authors' explanation for parahippocampal herniation Past history of herniation 4 shunt malfunction 1 external drainage of the cyst 2 unknown Shunt related hypotension Embryologically-related anatomic variant
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uncus. The anatomical presence of a rigid tentorium with a hiatus in it may facilitate the development of this kind of gradient, effective enough to create a chronic herniation. This phenomenon appears analogous to that of an acquired Chiari secondary to lumboperitoneal shunts [3]. Naidich et al. [8] pointed out that this phenomenon might reflect shunt malfunction. Although their series did not mention the objective evidence of a raised ICP, due to shunt blockage leading to a chronic phenomenon, we believe a negative pressure gradient with negativity toward posterior fossa is a mandatory prerequisite of the chronic finding. Hence, an association with malfunctioning lateral ventricular shunt may be a contributory event in selected cases, as in the Naidich et al. series [8]. Moreover, most supratentorial shunt malfunctions will lead to an acute or subacute clinical syndrome. If tentorial herniation occurs in these instances, full-blown acute brainstem compression will inevitably lead to coma and decerebration. Ng et al. had postulated that the parahippocampal herniation, which they observed, was related to herniation, from the suspected history of viral encephalitis “aggravated” by DWS [12, 13]. Unlike the patient described by Ng et al., interestingly, our patient had no history suggestive of herniation before the appearance of the radiological finding and symptoms. Repeated cranial CT in episodes of headache and diplopia showed no signs suggestive of shunt malfunction, and fundoscopy during these episodes did not show papilloedema. Horowitz et al. reported a 41-year-old man who presented with “atypical” trigeminal neuralgia [5]. Along with parahippocampal herniation, the imaging demonstrated Chiari malformation. There was also an extremely caudal transverse sinus and a low tentorium. They postulated that this combination might represent a congenital anatomical variant [5]. With the exception of the case reported by Horowitz et al. [5], the predisposition to chronic uncal herniation in shunted DWS and other cerebellar cysts is obvious. This complication being unreported in cerebellar astrocytoma resection may be due to the low frequency of CPS in this situation. Continuity of the shunted cystic space to fourth ventricle may be another prerequisite for the development of chronic uncal herniation, as is natural in DWS and postoperative in our patient (Fig. 2). This may be the reason that this complication has never been reported following CPS in treatment of a retrocerebellar arachnoid cyst [11]. Why the complication has been unreported in other recent series on treatment of DWS is unclear [7, 15]. Naidich et al. [8] noticed chronic cerebral herniation in seven (27%) of 26 patients. Can choosing a more conservative shunting system in selected patients prevent this complication? Our patient initially had a low-pressure valve with a partial positive
response following upgrading. It is advised therefore to use more restrictive hardware in similar cases. The symptomatologies associated with chronic cerebral herniation seem varied. Our patient had intermittent headache, vomiting, and diplopia, which can be explained by traction on pain-sensitive intracranial structures, meninges, and the abducent nerve [4, 9]. The patient reported by Ng et al. presented with a seizure. Ng et al. have successfully treated the seizure disorder (by surgical disconnection of hippocampus); shunt-related hypotension as a cause of seizures has been reported, albeit in only a few case reports [2]. One case reported by Horowitz et al. presented with trigeminal neuralgia. Such a facial pain may represent local irritation or traction on the fifth nerve. Naidich et al. [8] reported a difficult clinical course marked by multiple shunt revision. The phenomenon may be self-limiting in view of the limited volume of fourth ventricle. The implication here is that a collapsed fourth ventricle (as in Fig. 3) may no longer contribute to the phenomenon, thus relieving the clinical features. This may explain the episodic nature of the presentation as seen our patient. Chronic transtentorial herniation may be misinterpreted as a posterior fossa tumor [5] or a medial temporal lobe or ambient cistern mass lesion [8]. They are usually bilateral (80% in this series). Occasionally, high-resolution imaging may show deviation of the posterior cerebral artery around the herniation site [8]. The predisposing causative pathology may be suggestive, such as a CPS associated with DWS. The MRI in our patient, apart from the findings of uncal herniation, showed venous-engorgement-associated enhancement of the posterior fossa meninx, a slit-like fourth ventricle, and a relatively tight posterior fossa. These findings are analogous to the corresponding
Fig. 4 Cranial CT done 5 years back showed the same finding of parahippocampal herniation (arrows) without the presence of ventricular dilatation
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components in an over-shunted supratentorial ventricle with secondary intracranial hypotension syndrome [10, 14]. The slit-like fourth ventricle was probably secondary to the fourth ventricle being in continuity with the cystic space with a draining shunt tip (Fig. 3). These findings probably corroborate our postulation of a posterior fossa hypotension creating a secondary negative pressure gradient, relative to the supratentorial space. We noticed the phenomenon within a few months of insertion of the posterior fossa shunt, and the finding has been persistent (Fig. 4). Naidich et al. reported changes in the severity of herniation, with it varying relative to the success of the lateral ventricle decompression. They also reported complete disappearance of herniation in one patient [8]. Can chronic uncal herniation predispose to acute life threatening brainstem compression? A theoretical possibility of catastrophic consequence remains. Two out of the seven patients in Naidich et al. series died. It is unclear how contributory chronic cerebral herniation was to the event. Naidich et al. [8] opined that the finding might be a bad prognostic sign. We recommend that patients with such MR findings be handled cautiously. If asymptomatic, they can be followed. However, if symptoms persist or progress, treatment should be initiated. Situations where a patient is shunted, both supra- and infra-tentorially, and has uncal herniation can prove dangerous. In such a situation, supra-tentorial shunt malfunction may lead to increased downward displacement and acute brainstem compression. Upgrading the posterior fossa system according to the surgeon’s preference is a possibility in instances associated with isolated posterior fossa shunts.
Conclusions We postulate that chronic uncal herniation is a complication of posterior fossa shunting that occurs mostly in children with DWS or other cystic cavities that are in communication with the fourth ventricle. There may be a role of upgrading of the shunt system in symptomatic patients. In
instances where a lateral ventricular shunt is also present, the priority should be to rule out shunt malfunction.
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