Obstruction of the proximal catheter, excessive cerebrospinal fluid (CSF) draining, catheter migration, infection, and shunt fractures are all common causes of shunt malfunction [3, 5, 6, 12, 20]. Proximal catheter tip blockage is thought to cause 50% of all shunt problems two years after shunt insertion [6]. In addition, distal catheter occlusion has been linked to an additional 15–30% of shunt failure in afflicted individuals [6, 9]. Excessive CSF drainage after shunt insertion is another cause of shunt malfunction. Fast CSF diversion can cause extra-axial fluid accumulation, such as hygroma and subdural hemorrhage [9, 13]. Severe intracranial consequences such as seizures, autonomic instability, decreased school performance and decreased level of consciousness have been linked to excessive CSF drainage and shunt obstruction [6]. Another source of shunt malfunction is shunt disconnection, which is strongly linked to surgical errors [6, 12]. Other etiologies of shunt malfunction include catheter migration and shunt infections [3]. Several other studies have shown that shunt migration is more common in children than adults [3, 6, 21].
Children with shunt malfunction may present symptoms and signs consistent with high intracranial pressure and cranial nerve paralysis. Although cranial nerve palsies and their clinical manifestation has been substantially reported following shunt insertion [15, 22–31], they can be associated with shunt malfunction. Most cranial nerve involvement in shunt malfunction are papilledema decreased vision, 6th nerve palsy and diplopia [16, 32–34]. Sometimes cranial nerve damage can occur during surgery like our previous case of an infant who suffered peripheral facial nerve palsy following VP shunting. We found that the underdeveloped bony structures may have rendered the extracranial part of the facial nerve more vulnerable to blunt trauma [35]. In another study, Kumaria et al. reported a case of 7th palsy following VP shunting. They suggested a soft tissue injury during tunneling led to inflammation of the facial nerve distal to its cranial exit at the stylomastoid foramen which could be the likely cause of patient symptoms [26].
Although the pathophysiology of facial nerve palsy associated with shunt malfunction may be vague, Grossman and Feldman [16] observed that bone growth in some pathologies like osteopetrosis could lead to compression of the shunt valve at the proximal part of the ventricular catheter and so unilateral or bilateral obliteration of cranial nerve foramina that could result in facial paralysis and shunt obstruction. Thines et al. added that ventricular dilation could produce a slight downward herniation of the brainstem and increased stretching forces applied to both facial nerves, leading to facial diplegia [32]. More 7th palsy in our patients with myelomeningocele or Chiari type II history can be related to this physiopathology. Some authors found that facial and/or abducent nerve palsies also occurred after downward traction of the brainstem following a collapsed 4th ventricle or from pressure on the floor of the 4th ventricle by a shunt catheter tip [22, 24, 28, 29]. In addition, Maus et al. suggested mechanical irritation as the pathophysiology of facial nerve palsy in a patient with CSF over-drainage and intracranial hypotension [33]. Spennato et al. indicated that new cranial nerve deficits in children with posterior fossa shunts might indicate over-drainage [15].
Notably, ventricular dilation following shunt malfunction and uncal herniation may compress the oculomotor nerve leading to oculomotor nerve palsy and related symptoms like ptosis [16, 37]. Dadlani et al. reported a rare case of bilateral oculomotor nerve palsy in which the patient presented with bilateral ptosis and decreased visual acuity. Subsequent investigations showed shunt disconnection [36].
In this series, three patients presented with ptosis, with one patient (case 6) having an additional contralateral frozen eye, a symptom consistent with bilateral oculomotor nerve palsy associated with 6 palsies. An extensive series by Razmara and Jackson [2] identified oculomotor palsies as the strongest indicator of shunt malfunction. Therefore, the presence of this sign should trigger clinical suspicion of shunt malfunction in children with a history of shunt placement. In this series, two patients had dystonia and torticollis; to our knowledge, these symptoms have never been reported in the literature. Both cases had post-fossa pathologies, including Chiari type II in case 2 and DWS in case 8. Shunt malfunction with increased intracranial pressure induced lower cranial nerves like 11th nerve distraction or retraction due to hindbrain herniation. Table 2 illustrate case reports/series of odd presentation associated with shunt malfunction in the literature.
Table 2
Case reports/series of odd presentation associated with shunt malfunction
Authors/year | Patient No. | Age (years)/Sex | Type of usual case (s) | Underlying disease | Age first shunted | Previous shunt revision | Intervention | Outcome | Comment |
Ramsey et al./2006 [29] | 1 | 9/F | Bilateral CN VI palsy | N/S | N/S | N/S | No shunt revision | Improved | Due to additional visual loss symptoms optic nerve sheath fenestration was performed |
Tan et al./2015 [32] | 1 | 15/F | CN VI palsy, diplopia | Suprasellar arachnoid cyst, hydrocephalus | N/S | No | Non-function distal catheter replacement, no shunt revision | Improved | Slit-like ventricle was observed |
| | | | | | | | | Holocord syrinx observed on MRI |
Elliott et al./2009[31] | 2 | 16/M; 14/M | Tetraparesis, bilateral CN VI, CN VII palsies; Medial deviation of left eye, left peripheral Facial paresis, CN VI palsy, limb ataxia, vocal cord paralysis | Cerebral palsy, hydrocephalus; Communicating hydrocephalus | After birth; 4 months old | N/S; Yes | Shunt revision; Shunt revision surgery revealed decreased flow across the valve | Both improved | Additional surgery for underlying Chiari malformation 1 |
Maus et al./2011 [26] | 1 | 18/M | diplopia, papilledema + Isolated mild right sided facial palsy + subsequent left sided facial palsy | Arachnoid cyst + hydrocephalus | 8 year old | No | Shunt revision | Improved | Two days postoperatively, the patient developed an isolated mild facial palsy on the right side (opposite to the site of the arachnoid cyst; House–Brackmann grade II), which deteriorated. He experienced decreased ICP (opening pressure > 120 mmH2O). Bilateral facial palsy regressed and improved after opening pressure was readjusted to > 140 mmH2O. |
Thine et al./2007 [33] | 1 | 15/M | Facial diplegia, Other symptoms included: Headache, Nausea | Obstructive hydrocephalus, Crouzon syndrome, tonsillar herniation | 1 year old | No | Shunt revision surgery revealed complete catheter obstruction | Improved | |
R Grossman and Z Feldman/2004 [16] | 1 | 9/M | Bilateral facial nerve paralysis, deafness, blindness | Cranial mass, increased ICP | 8 year old | No | Shunt revision | Improved | |
Dadlani et al./2015 [23] | 1 | 6/M | Bilateral ptosis and limited ocular movement due to oculomotor palsy Other symptoms included fever | Myelomeningocele | N/S | N/S | Patient was given new shunt due to ventricular dilation. An attempt to remove the old shunt. Operative findings revealed shunt discontinuation | Improved | Had a history of visual acuity and bilateral ptosis. Upon examination, CSF revealed florid eosinophilia and elevated protein level but normal CSF sugar levels. Sputum culture grew Staphylococcus aureus and steroids, antifungal and antibiotics were started empirically. |
M; male, F; female, CN; cranial nerve, VP; ventriculoperitoneal, ICP; Intracranial pressure, IVH; Intraventricular hemorrhage, ICH; Intracranial hemorrhage, N/S; not specified. Note: The common symptoms and signs of shunt malfunction in the various cases that were not deemed odd in presentation and adult cases were excluded. |
Although the theory is still debated [38–43], Lucas et al. believe that increased intracranial pressure may disrupt subcortical-cortical interconnections, allowing seizures to occur [7]. According to our knowledge, although seizures may not be classified as rare shunt malfunction-associated symptoms, they can occur together with odd symptoms, as demonstrated in case 6 in our series. Regarding seizures, Bourgeois et al. [44] found that patients with a previous history of epilepsy often had seizures (either new onset or with previous history) during shunt malfunction. According to their results, seizures were the presenting symptom in 28% of shunt malfunctions in patients with a previous history of epilepsy. In contrast, seizure as a presenting symptom only occurred in 3% of children without such a prior history [44]. Gonzalez et al. also identified chronic seizure as an independent factor associated with shunt malfunction [45]. Furthermore, this symptom has been associated with multiple shunt revision [46], VP shunt over-drainage [47] and intracranial hypotension [48].
Shunt malfunction is generally confirmed by a combination of a shunt tap with elevated intracranial pressure and a head CT or ultrasound scan showing ventricular dilation. However, imaging alone may not demonstrate an increase in ventricular size despite shunt malfunction. This situation is true particularly when shunt malfunction is intermittent. To assess the diagnostic yield of evaluation for shunt malfunction in patients with intraventricular shunt and seizure, Cohen et al. found that although a head CT scan was performed in 95.2% of the patients, only 10.6% of the scans were suggestive of shunt malfunction [49]. They concluded that imaging studies were low yielded for evaluating shunt malfunction in children with intraventricular shunt and seizures [49]. In a series of 15 patients with shunt malfunction [50], Faillace et al. observed changes in ventricular size in 11 and an increase in the porencephalic cyst in two patients. Of three patients in whom shunt tap pressure was recorded, two had normal pressure with less than 150 mm H20, and one had increased pressure. Among the six cases whose intraventricular pressure was measured intraoperatively, five had elevated pressure. These findings indicate that normal CSF pressure may rarely be presented with shunt malfunctions [7]. Shunt malfunction should be considered in any patient with a previous shunt and either usual or unusual new symptoms. Clinical examination, brain imaging, shunt series radiography, very close observation, intracranial pressure monitoring, and shunt tap are all steps that, in combination, could help neurosurgeons to make the best decision with less complication.