Odd presentation of shunt malfunction: a case series and review of literature

Children with previous ventriculoperitoneal shunt (VPS) insertion due to hydrocephalus may refer to the hospital with various clinical complaints. Shunt malfunction is frequently diagnosed in these children necessitating shunt revision. Although increased head circumference, setting sun eye in younger children, and headache, nausea/vomiting, loss of consciousness, visual disturbance, and other signs of intracranial hypertension are common clinical manifestations of shunt malfunction, some patients may present with odd or unusual symptoms. Here, we present a series of patients with shunted hydrocephalus who presented with odd and unexpected clinical manifestations of shunt malfunction. Eight children with shunt malfunction were enrolled in this series. The age, sex, age of shunting, etiology of hydrocephalus and management, post-shunt insertion symptoms/sign, revision surgery, outcome, and follow-up were evaluated. Patients were aged from 1 to 13 years (mean, 6.38 years). There were 5 males and 3 females. The odd presentation associated with shunt malfunction included facial palsy in three children, ptosis in 3 children, and torticollis and dystonia each in one child. All patients underwent shunt revision except for one patient in whom a new shunt was inserted. Follow-up showed improvement of the symptoms in all patients. In this series, we reported eight patients with unusual signs and symptoms following shunt malfunction that were successfully diagnosed and managed.


Introduction
Ventriculoperitoneal shunt (VPS) is considered as the standard treatment for hydrocephalus. Despite its effectiveness, VPS has been associated with significant complications, including shunt malfunction and infection [1]. Approximately 35% to 40% of shunts are diagnosed with malfunction by the first year after insertion [2][3][4]. Most shunt malfunctions occur due to mechanical obstruction of the shunt system. Tissue debris, fibrosis, and choroid plexus in the catheter may result in proximal obstruction, while clogging, kinking, thrombosis, or venous occlusion may lead to distal obstruction [5,6]. Also, excessive fluid drainage, migration, and resultant discontinuation of the shunt catheter, infection, and shunt fracture are other significant shunt malfunction etiologies [3,6].
The diagnosis of shunt malfunction is usually based on clinical symptomatology and relative ventriculomegaly on brain imaging associated with increased intracranial pressure. However, stable ventriculomegaly on computer tomography (CT) imaging may be incorrectly construed as proof of normal shunt function [7].
The clinical presentation of shunt complications may vary from nonspecific symptoms such as fever, lethargy, headache, nausea and vomiting, gastrointestinal, and musculoskeletal symptoms to severe symptoms including ataxia, seizures, autonomic instability, or even coma [8][9][10][11][12][13][14]. There are rare cases in which clinical presentations may be unusual or odd [15][16][17] leading to misdiagnosis or delay in diagnosis and treatment. Several reports have demonstrated the essential role of clinical predictive models that necessitate early diagnosis and ensure immediate intervention for shunt malfunction [2,10,18,19]. Nonetheless, the wide variability in clinical presentation observed in patients with shunt malfunction can result in misdiagnosis, postpone the appropriate intervention and increase the morbidity and mortality.
In this study, we present eight patients with shunted hydrocephalus that were referred to our neurosurgical department with an odd clinical presentation. To further expound on these rare cases, we reviewed the literature. The mechanism, clinical presentation, diagnostic approach, management, and prognosis of these unusual cases are discussed in detail.

Patient demographic
A retrospective review of the medical records of the patients who presented with an odd presentation of shunt malfunction at Children's Hospital Medical Center in Tehran from June 2015 to February 2022 was performed. Eight patients with a previous history of shunt placement for hydrocephalus were included in this series. The age and sex of patients, etiology of hydrocephalus and history of VPS, clinical presentation, shunt revision, and follow-up period were evaluated.

Results
Eight children, including 5 males and 3 females, were enrolled in this case series ( Table 1). The patients' ages ranged from 1 to 13 years (mean, 6.38 years). The etiology of hydrocephalus was due to myelomeningocele (3 cases), Dandy-Walker syndrome (2 cases), congenital obstructive hydrocephalus (2 cases), and post-hemorrhage (1 case). Seven patients underwent VPS placement, and a cystoperitoneal shunt was inserted for one patient. The age at shunt placement ranged from 1 to 10 months (mean, 4 months).
Of the eight patients with shunt malfunction, the clinical presentation showed facial palsy in three patients (cases 4, 5, and 7), ptosis in three patients (cases 1, 3, and 6), torticollis in one patient (case 8), and dystonia in one patient (case 2). Case 6 also had contralateral frozen eye and seizures which progressed to loss of consciousness before shunt revision. Other symptoms in addition to these unusual signs at presentation were occasional headache, nausea, and papilledema. Nevertheless, all 8 patients initially presented with those unusual manifestations.
Neuroimaging, including brain computer tomography (CT) scan and magnetic resonance imaging (MRI), was performed in all patients to rule out any associated pathologies like tumor abscess or vascular abnormalities that can cause 3rd, 7th, and 11th cranial nerve palsies.
Radiological studies to assess the shunt apparatus included shunt series, brain CT scan or MRI, and abdominal ultrasound. Brain imaging confirmed increased ventricular size in 7 patients and slit-like ventricle in one case. Proximal shunt malfunction was the cause of symptomatology in 7 patients, and pseudocyst of abdomen was the source of complaints in one case. Shunt tapping was performed in case of slit ventricle that no fluid was drained. Intracranial pressure monitoring was not used for evaluation of the patients in this series.
All patients underwent shunt revision surgery except one who underwent new shunt placement (patient with distal shunt infection and pseudocyst of abdomen). Clinical improvement of signs and symptoms was observed in all patients after revision surgery.

Discussion
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 2 years after shunt insertion [6]. In addition, distal catheter occlusion has been linked to an additional 15-30% of shunt failures [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 pitfalls [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 have been substantially reported following shunt insertion [15,[22][23][24][25][26][27][28][29][30][31], they can be associated with shunt malfunction. Most cranial nerve involvement in shunt malfunction is papilledema decreased vision, 6th nerve palsy, and diplopia [16,[32][33][34]. Sometimes cranial nerve damage can occur during surgery like our previously published 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]. Kumaria et al. reported a case of 7th cranial nerve palsy following VP shunting. They suggested that 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 could cause 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]. Facial nerve palsy in our patients with myelomeningocele and Chiari type II can be related to this pathophysiology. 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 the present series, three patients presented with ptosis, with one patient (Table 1, case 6) had an additional contralateral frozen eye, a symptom consistent with bilateral oculomotor nerve palsy associated with abducens 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 shunt. Dystonia was found in one child, and torticollis was observed in another patient in this series. To our knowledge, these symptoms have never been previously reported in the literature as signs of shunt malfunction. Both patients had posterior fossa pathologies, including Chiari type II in case 2 and Dandy-Walker syndrome in case 8. The possible explanation in these cases could be the shunt malfunction with increased intracranial pressure-inducing traction to the lower cranial nerves like 11th nerve due to hindbrain herniation.
Although the theory is still debated [38][39][40][41][42][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 other unusual symptoms, as demonstrated in case 6 in our series (Table 1). 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  [45]. Furthermore, seizure has been associated with multiple shunt revision [46], VP shunt over-drainage [47], and intracranial hypotension [48]. Table 2 presents previously published case reports and series of cases with odd presentation associated with shunt malfunction. Shunt malfunction is generally confirmed by a combination of a shunt tap, demonstrating elevated intracranial pressure and a head CT or ultrasound scan showing ventricular dilation. Shunt tapping potentially carries risk of shunt infection and should be reserved for doubtful cases in whom definite diagnosis cannot be made by imaging and clinical evaluations. In such cases, dry tap can confirm proximal catheter failure, while easily CSF drainage from the reservoir which followed by rapid clinical improvement can imply distal malfunction. When the diagnosis of shunt malfunction is severely in doubt, particularly if the clinical and radiologic findings are not straightforward, continuous intracranial pressure monitoring can be a beneficial confirmatory diagnostic trial. However, there is not always 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 rarely found in 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, close observation, intracranial pressure monitoring, and shunt tap are all steps that, in combination, could help neurosurgeons to diagnose and treat shunt malfunctions on time.

Conclusion
Because of the wide variation in clinical presentation among patients, CSF shunt malfunction can be misdiagnosed. A thorough examination of patients with shunts is required to ensure an early and accurate diagnosis of shunt malfunction which is important to avoid concomitant morbidity and mortality. We described unusual presentations of shunt malfunction in eight patients with primary symptoms including facial nerve palsy, ptosis, dystonia, and torticollis.