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Year : 2016  |  Volume : 19  |  Issue : 4  |  Page : 510-511

Bilateral abducens and facial nerve palsies as a localizing sign due to reduction in intracranial pressure after fourth ventriculoperitoneal shunting

1 Department of Neurology, Aster Neurosciences, Aster Medcity, Kochi, Kerala, India
2 Department of Neurosurgery, Aster Neurosciences, Aster Medcity, Kochi, Kerala, India

Date of Submission11-Mar-2016
Date of Decision27-May-2016
Date of Acceptance29-Jul-2016
Date of Web Publication21-Nov-2016

Correspondence Address:
Boby Varkey Maramattom
Department of Neurology, Aster Neurosciences, Aster Medcity, Kochi - 682 023, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-2327.194457

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A trapped fourth ventricle often requires fourth ventriculoperitoneal shunting (4VP). Complications of this procedure include shunt blockage, infection, shunt migration, and overdrainage. Cranial nerve palsies are very rare after 4VP shunting and have been described with over drainage and brainstem distortion. We present an unusual case of bilateral abducens and facial nerve palsies after 4VP shunting after normalization of 4 th ventricular parameters. Measurement of various brainstem angles presented us with a plausible hypothesis to explain the cranial nerve dysfunction.

Keywords: Bilateral abducens and facial nerve palsy, cranial nerve palsy, fourth ventriculoperitoneal shunting, postshunting cranial nerve palsy, postshunting palsy

How to cite this article:
Maramattom BV, Panikar D. Bilateral abducens and facial nerve palsies as a localizing sign due to reduction in intracranial pressure after fourth ventriculoperitoneal shunting. Ann Indian Acad Neurol 2016;19:510-1

How to cite this URL:
Maramattom BV, Panikar D. Bilateral abducens and facial nerve palsies as a localizing sign due to reduction in intracranial pressure after fourth ventriculoperitoneal shunting. Ann Indian Acad Neurol [serial online] 2016 [cited 2023 Feb 3];19:510-1. Available from:

   Introduction Top

"False localizing signs" (FLS) reflect dysfunction distant or remote from the expected anatomical locus of pathology often in the context of raised intracranial pressure (ICP) or spinal cord lesions. [1] Abducens nerve palsies are the most common intracranial FLS followed by facial nerve palsies. These occur due to nerve traction or brainstem displacement by intracranial lesions. [2] We present an unusual case where bilateral abducens and facial nerve palsies and Parinaud's syndrome occurred due to brainstem shift after the fourth ventriculoperitoneal (4VP) shunting.

A 16-year-old girl presented to us 1 month after 4VP shunting with decreased facial expressions. Her symptoms had started 1 week postoperatively but were slowly improving. She had a history of postmeningitic hydrocephalus with multiple revisions of VP shunting and a recent trapped fourth ventricle. On examination, she had upgaze and convergence restriction, normal pupil reactions and bilateral 6 th and 7 th lower motor neuron palsies. Facial nerve conductions were normal, but blink reflexes were absent bilaterally. A magnetic resonance imaging brain showed normalization of 4 th ventricular size and change in brainstem angles [3],[4] [Figure 1]. After 4VP shunting, the posterior translocation of the brainstem was greatest at the level of the pons (1.13 cm). As she was clinically improving, shunt revision was deferred.
Figure 1: (a and b) Sagittal magnetic resonance imaging T2-weighted images. The brainstem tentorial angle change from 33 (preoperative) to 25 (postoperative). (c and d) Axial T2-weighted magnetic resonance imaging images at the mid-pontine level

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Surgical treatment of a trapped fourth ventricle usually involves 4VP shunting. Shunt complications include shunt malfunction, infection, shunt dislocation, and over drainage. There are only a few reports of cranial nerve palsies following 4VP shunting with collapsed 4 th ventricles, and distortion of the brain stem and all cases have required revision surgery. [5],[6]

Clinically, our child had a partial Parinaud's syndrome and bilateral 6 th and 7 th nerve palsies. The Parinaud's syndrome was likely secondary to mesencephalic distortion. The 6 th and 7 th nerve palsies were most likely due to traction as the brainstem abruptly moved backward after 4VP as there was no pontine injury or 4 th ventricular collapse and the shunt position was adequate. The brainstem angles in our patient demonstrated a significant brainstem correction with the greatest posterior displacement of the pontine portion of the brainstem. It is known that slow-growing tumors can greatly distort the facial nerve without any clinical manifestations. However, in our child, the abrupt change in intracranial dynamics and sudden traction of the cranial nerves are the most likely causative of the cranial palsies. The abnormal blink reflex studies also corroborate a proximal facial nerve injury. The spontaneous improvement is a testament to the remarkable cranial nerve plasticity.

Our case is a queer example of a localizing sign due to paradoxical normalization of ICP, rather than an FLS of raised ICP.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Larner AJ. False localising signs. J Neurol Neurosurg Psychiatry 2003;74:415-8.  Back to cited text no. 1
Maurice-Williams RS. Multiple crossed false localizing signs in a posterior fossa tumour. J Neurol Neurosurg Psychiatry 1978;38:1232-4.  Back to cited text no. 2
Shah LM, McLean LA, Heilbrun ME, Salzman KL. Intracranial hypotension improved MRI detection with diagnostic intracranial angles. AJR Am J Roentgenol 2013;200:400-7.  Back to cited text no. 3
Volpe P, Contro E, De Musso F, Ghi T, Farina A, Tempesta A, et al. Brainstem-vermis and brainstem-tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis. Ultrasound Obstet Gynecol 2012;39:632-5.  Back to cited text no. 4
Pang D, Zwienenberg-Lee M, Smith M, Zovickian J. Progressive cranial nerve palsy following shunt placement in an isolated fourth ventricle: Case report. J Neurosurg 2005;102 3 Suppl: 326-31.  Back to cited text no. 5
Spennato P, O'Brien DF, Fraher JP, Mallucci CL. Bilateral abducent and facial nerve palsies following fourth ventricle shunting: Two case reports. Childs Nerv Syst 2005;21:309-16.  Back to cited text no. 6


  [Figure 1]

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