Introduction

The migration of ventriculo–peritoneal shunt catheter is a rare complication of surgical treatment for hydrocephalus. The migration may be in either direction and is more frequent with hard and spring loaded shunt tubes ,₂.

The authors report a case of intracranial dislocation of a ventriculo–peritoneal shunt catheter. The pathophysiological mechanism of the catheter migration is discussed.

Case Report

A male child was born by breech delivery at the 30^th week of gestation. Four months later it developed macrocephalia and a tense fontanel.

Computed Tomography: increase of ventricular volume. The child underwent a ventriculoperitoneal shunt (medium pressure). On the 9^th postoperative day, the child was discharged. Some days later, the child returned to João Alves Filho Hospital (Aracaju – Sergipe – Brazil), with signs and symptoms of increased intracranial pressure and with dehydration, macrocephalia, tense fontanel and a tumor in the right posterior parietal region.

Computed Tomography: increase of ventricular volume and air in the right temporal horn and shunt tube in the cranium. (Figure 1). The child underwent surgical removal of the tube and a new tube was implanted on the contralateral side. On the 7^th postoperative day, the child discharged. Nowadays, the child had been treated with anticonvulsivant drugs and ambulatory follow–up.

Figure 1

Figure 1: Computed tomography showing intracranial shunt catheter.

Discussion

Shunt complications have been frequently reported in literature. The intracranial migration of ventriculo–peritoneal shunt is the most rare complication and constitutes 0,1% to 0,4% of all shunt procedures ₁. Distal migration of the shunt has often been reported ₁,₂,₃,₄,₁₁. The pressure gradient between the cranial and peritoneal cavities decides the direction of migration ₆,₁₂. The mechanism of shunt migration involves adhesion, necrosis, penetration, perforation, migration and extrusion ₆,₈,₁₃.

Two principal causes have been suggested to explain the shunt migration into the cranium: the mechanic force moving the shunt catheter into the cranium and the low resistance ₆,₁₃. In childhood, vigorous flexion–extension movements of head may act as a windlass, facilitating upward migration of the shunt catheter ₁₀. Over and above that, the distance between the ventricular and the peritoneal ends of the catheter is smaller than in adults, and proximal migration is easier ₁₃.

Shimizu et al ₁₃reported a case with visual shortage and seizures. Those authors suggested that the cause of migration shunt catheter had been related to stress due to seizures, constipation and osteolysis insulted by craniotomy. Gupta & Mann ₈ reported a case of shunt migration in a child with Dandy Walker cyst. Absence of raised intracranial pressure in this case suggests equilibration of cerebrospinal fluid pressure gradient. The diagnosis was incidental and the patient can be followed up expectantly. Cerrón-Rojas et al ₅reported a case of simultaneous cephalic migration into the intraventricular and subdural spaces. Those authors concluded that some factors are necessary such as detachment of the shunt of the distal end (technical fault), underlying disease (porencephaly), dynamic factors causing expulsion (abdominal peristaltic movements), dynamic translocation factor (neck movements), dynamic attraction factor (increased cerebrospinal fluid reabsorption) and unishunt catheter (offering no resistance to passage through the trepanation orifice) ₅. Technical fault is reported as cause of migration by others authors ₆,₈.

The treatment consists on removing the migrated shunt and implantation of a new shunt, preferably with a reservoir ₁,₉. Migration of a shunt is not prevented by locks and slip clips ₇,₈.

Correspondence to

Dr. Carlos Umberto Pereira, M.D. Augusto Maynard Avenue, 245/404 49015-380 Aracaju – Sergipe, Brazil Tel: 55 + 79 + 2130518 e-mail: umberto@infonet.com.br