Shunt Overdrainage: Reappraisal of the Syndrome and Proposal for an Integrative Model

Abstract

Although shunt overdrainage is a well-known complication in hydrocephalus management, the problem has been underestimated. Current literature suggests that the topic requires more examination. An insight into this condition is limited by a lack of universally agreed-upon diagnostic criteria, heterogeneity of published series, the multitude of different management options and misunderstanding of relationships among pathophysiological mechanisms involved. We carried out a review of the literature on clinical, radiological, intracranial pressure (ICP), pathophysiological and treatment concepts to finally propose an integrative model. Active prophylaxis and management are proposed according to this model based on determination of pathophysiological mechanisms and predisposing factors behind each individual case. As pathophysiology is progressively multifactorial, prevention of siphoning with gravitational valves or antisiphon devices is mandatory to avoid or minimize further complications. Shunt optimization or transferal and neuroendoscopy may be recommended when ventricular collapse and cerebrospinal fluid isolation appear. Cranial expansion may be useful in congenital or acquired craniocerebral disproportion and shunting the subarachnoid space in communicating venous hydrocephalus and idiopathic intracranial hypertension.

Risk factors, treatment, and outcome in dogs and cats with subdural hematoma and hemispheric collapse after ventriculoperitoneal shunting of congenital internal hydrocephalus

“…Prevalence of overshunting related complications such as hemispheric collapse and subdural hematoma was 18% (Cl 95% 9.9‐26.66) among the animals treated with VPS in this study. This is similar to other reported complication rates in veterinary and human medicine 1,2,7,8 …”

“…The impact of the hydrostatic force within the shunt depends on the distance between the intraventricular and peritoneal cavities. 7 This distance is much lower in dogs, especially in toy-breed dogs and cats, which could explain the missing benefit for differential valves in animals. The positioning of the gravitational valve system might play an important role as it affects the function of CSF drainage in the standing human where it is placed in a parallel line to the vertebral column.…”

“…Overshunting is also a well-known complication in human neurosurgery, which occurs in 10%-18% of patients treated with VPS. 7,8 In children, posthemorrhagic hydrocephalus, aqueductus stenosis as well as VPS placement in the first months of life, [9][10][11] neonatal meningitis, [11][12][13] and implantation of low pressure opening valves are common risk factors. 9,14,15 In adults, overshunting mostly occurs after changing from a lying into a standing position, when the hydrostatic pressure in the vertical catheter causes a siphon effect.…”

Incidental and Clinical Significance of Slit Ventricles in Fixed Pressure Valves

“…The last theory is venous hypertension theory, which results from diffuse meningeal venous hyperemia and engorgement of venous sinuses. Hence, it increases elasticity and stiffness as this depends mainly on the functioning of the cerebral venous outflow mechanism [ 12 ].…”

A case of hydrocephalus confounded by suprasellar arachnoid cyst and concomitant reversible cerebral vasoconstriction syndrome

“…However, programmable valves allow clinicians to increase the valve's opening pressure and subsequently reduce CSF drainage restoring a balanced flow. [16]…”