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Cerebrospinal Fluid Diversion Procedures: Ventriculo-Atrial, Ventriculo-Peritoneal, Ventriculo-Pleural, and Lumbo-Peritoneal Shunts
Hydrocephalus is a medical condition characterized by a pathologic dilatation of the ventricular system and the subarachnoid space due to an abnormal increment of the cerebrospinal fluid (CSF volume). This condition can be secondary to a blockage in the regular transit between the ventricles, blockage of the outlet of the ventricular system (non-communicating hydrocephalus), or secondary to an imbalance in the production/reabsorption of CSF (communicating hydrocephalus). Multiple lines of treatment for the management of hydrocephalus have been proposed including medical and surgical strategies. Nonetheless, surgical CSF diversion procedures have shown superiority as a long-term treatment and have been considered the treatment of choice since the 1950s. , Diversion techniques are mainly used in hydrocephalus but have also shown benefits when treating other CSF disorders such as idiopathic intracranial hypertension (IIH), subdural collections, and intracranial cysts.
Different diversion techniques have been developed since 1905, including intracranial bypass ventricular septostomy, and third ventriculostomy, which are techniques mostly utilized in the presence of obstructive (non-communicating) hydrocephalus. Extracranial CSF shunting with the implantation of valvular systems with drainage from the intraventricular space to an extracranial space is another type of CSF diversion. Extracranial shunting is commonly used in patients with communicating hydrocephalus but is still an option in cases of obstructive (non-communicating) hydrocephalus that failed treatment with intracranial endoscopic bypasses.
An optimal diversion treatment is the one that warrants a permanent CSF drainage/flow after a single surgical intervention. Nonetheless, complications and reinterventions associated with any type of CSF diversion procedure still occur despite technological advances and optimization in hardware and implantation techniques, with patients requiring at least one revision surgery in their lifetime.
This chapter focuses on the description of the different extracranial CSF shunting techniques with the implantation of valvular systems. We will also address the medical criteria behind the decision-making when choosing a specific shunting technique based on the clinical presentation, etiology, anatomical findings, and medical/surgical history. Intracranial endoscopic bypasses are further addressed in a different chapter.
Extracranial Cerebrospinal Fluid Diversion with Implantation of Valvular Systems
Extracranial CSF diversion was first developed in 1905 by Kausch with the implantation of a catheter from the intracranial ventricular space to the abdominal peritoneal space for CSF diversion and absorption, but was abandoned for more than 30 years due to lack of success. , ,
Later on, development of valvular systems consisting of a proximal catheter connected to a valve that regulates the volume of diverted fluid, along with a distal catheter, drastically improved success rates. , , The proximal catheter is usually implanted in the frontal or occipital ventricular horns in the non-dominant cerebral hemisphere with no reported significant differences between these implantation sites. , The distal catheter then goes from the valve to an extracranial space where CSF is reabsorbed. Depending on the implantation site of the distal catheter, we can classify the extracranial diversion techniques as ventriculoatrial (VA) if the distal catheter is implanted in the right hearth-atrium, ventriculoperitoneal if the distal tip is implanted in the abdominal peritoneal space, and ventriculopleural (VPl) if implanted in the thoracic pleural space. There is an additional extracranial diversion technique, known as lumbar-peritoneal shunt, that does not access the ventricular system that consists of the insertion of a proximal catheter in the lumbar subarachnoid space and the implantation of a distal catheter in the abdominal peritoneal space.
Ventriculoatrial Shunt
The first successful report of a VA shunt was documented by Nulsen and Spitz in 1952 as treatment in a patient with hydrocephalus, and this was widely used in the 50s and 60s among the surgical community. VA shunting has also been associated with cardiovascular complications that are potentially life threatening, which led the majority of surgeons to use this procedure only when other techniques have failed or are contraindicated. Nonetheless, the vast majority of reported complications are the result of studies with a predominant pediatric population. , , , Hung et al. recently reported one of the largest retrospective studies in adult patients with idiopathic normal pressure hydrocephalus treated with VA shunts as the primary treatment with zero cases of associated cardiovascular complications. Two cases of nephritis were reported in this study with no conclusive association that indicated the VA shunts as causative. Other known complications were either comparable or lesser when compared with VP shunts. Other studies have found similar results with equal complication rates when compared with VP shunts. , There has been increasing utilization of this technique by surgeons in recent years due to the growing number of reported studies showing VA shunting as a safe first option when shunting is required in patients with hydrocephalus. ,
Indications
Patients with hydrocephalus in which a permanent CSF diversion is required. Although this technique can be used as the first-line approach, it is of special consideration in cases with previously complicated peritoneal placements or cases with multiple abdominal surgical procedures with subsequent peritoneal adhesions, history of peritonitis, severe ascites, and multiple distal peritoneal catheter obstruction/malfunction. , , , ,
Surgical Procedure
The patient is placed under general anesthesia with endotracheal intubation and positioned supine with a slight Trendelenburg to decrease risk of air embolism, head rotated toward the contralateral side of the planned incision. Entry site and tunneling areas are shaved if necessary, then prepped and draped. Preoperative administration of intravenous prophylactic antibiotics against staphylococcus 30 minutes before incision is recommended. Local anesthesia is injected along the areas of the planned incision. Different approaches for the placement of the proximal catheter can be utilized including the frontal approach that consists of a burr hole over the Kocher point located ∼1 cm anterior to the coronal suture and 2 to 3 cm lateral to the midline. The catheter is then inserted into the frontal horn of the lateral ventricle to avoid the choroid plexus that has a more posterior location. An alternative approach to the same lateral anterior horn can be achieved through a parieto-occipital burr hole. The proximal catheter can also be placed in the atrium of the ventricle with a parietal approach Fig. 82.1 . The selection of the approach is based on the conditions of the scalp, identification of previously implanted hardware, ventricle anatomy, and surgeon’s preference. We recommend preparing the ventricular and the jugular access followed by the tunneling toward the proximal incision, before proximal and distal catheter insertions.
Proximal Approach Preparation
In the frontal approach, a curvilinear incision overlying the Kocher point is performed to avoid superimposition of the hardware implant. An additional incision is needed at the retro auricular or cervical level to facilitate the tunneling process.
The authors’ preferred proximal approach is the parieto-occipital with the entry point located 6 cm above the inion and 3 cm lateral to the midline. A single curvilinear retro auricular incision superior and posterior to the pina is performed. Skin incision with a number 10 scalpel blade is carried out followed by subcutaneous tissue and galea dissection with electrocautery and special attention for pericranium preservation. A subgaleal pocket is then created for the implantation of the valve and reservoir hardware. After verification of the trajectory with neuro-navigation the parietal bone is then exposed and the burr hole is performed.
Distal Approach Preparation
Both external and internal jugular veins can be used for the implantation of the distal catheter. The external jugular vein is more commonly used given the proximity to the surface. The jugular vein and the carotid artery are located with ultrasound, ideally 3 and 4 cm respectively over the superior border of the clavicle and medial to the internal edge of the sternocleidomastoid muscle. The skin over the jugular vein is incised and the subcutaneous tissue is dissected until the platysma is reached. Neck incision is also used as the entry point for the distal catheter tunneling toward the proximal retro auricular incision.
Jugular Vein Access and J-Guidewire Insertion
Under ultrasound guidance, an 18-gauge needle attached to a 10-mL syringe is then introduced medially to the sternocleidomastoid with a lateral orientation into the internal jugular lumen with a continuous aspiration until venous blood return is obtained. Upon confirmation of proper jugular luminal localization the syringe is removed and the metallic tip of a J-guidewire is passed through the needle and advanced until changes in the electrocardiogram readings are noticed indicating an atrial localization of the J-guidewire. The guidewire is slightly pulled back, the needle is removed, and the guidewire is secured. The distal catheter is then tunneled toward the proximal retro auricular incision.
Ventricular Insertion of the Proximal Catheter
The previously exposed dura at the burr hole is opened in a cruciate fashion and coagulated with a Bovie at power of 18 followed by a gentle coagulation of the pia-arachnoid over the cortex with a bipolar cautery. Authors at this point change gloves before manipulating the valvular hardware and catheters to minimize contamination risks. The proximal and distal catheters are connected to the valvular system and functionality is checked. Authors recommend the placement of the ventricular catheter under CT-based neuro navigation guidance to achieve the best trajectory. Navigation stylet is inserted into a 9 French peel-away sheath, then gently advanced into the lateral ventricle with real-time trajectory monitoring. After optimal placement, the stylet is removed, and the peel-away sheath is held in place. The proximal catheter with a length ∼9 cm for the parieto-occipital approach is inserted into the sheath until reaching optimal location. Peel-away sheath is then stripped away, and the valve is anchored to the pericranium with 4-0 Nurolon sutures. Pumping of the valve is performed to confirm its appropriate refill and patency with CSF exit from the tip of the distal catheter.
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