Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4446_Библиотеки_им_академика_М_И_Перельмана

CTC is performed by instilling intrathecal non­ionic myelographic iodinated contrast (uores­cein). Sinuses are scanned both in prone and supine position. There is increase in >50 Hounseld units around the osseous defect in positive study around site of leak (Fig.29.1).

After diagnosing CSF rhinorrhea by beta-2 transferrin, next is localization of the skull base defect and site of CSF stula. High-resolution computed tomography (CT) is the initial radio­graphic test of choice, allowing for evaluation of the bony integrity of the skull base and paranasal sinuses. Patients with spontaneous CSF leaks have characteristic CT ndings that support the diagnosis. The bone of the skull base is broadly attenuated and thin. Arachnoid pits secondary to the bony impressions from the arachnoid villi in the skull base are present in 63% of patients with spontaneous CSF leaks. The most common sites of skull base dehiscence are the lateral recess of the sphenoid and the ethmoid roof. Pneumatization of the lateral recess of the sphenoid is reported in 91% of patients with spontaneous CSF leaks, in comparison with 23–43% in normal patients [12]. Dehiscence of the ethmoid roof or cribri­form plate is seen in 14% of patients with sponta­neous CSF leaks [13]. The presence of multiple skull base defects is common and may be present in 31% of these patients.

Approximately 80% of CSF leaks result from nonsurgical trauma, 16% from surgical proce­dures, and the remaining 4% are nontraumatic. Of the traumatic leaks, more than 50% are evi­dent within the rst 2days, 70% within the rst week, and almost all present within the rst 3months. Delayed presentation may result from wound contraction or scar formation, necrosis of bony edges or soft tissue, slow resolution of edema, devascularization of tissues, posttreat­ment tumor retraction, or progressive increases in intracranial pressure (secondary to brain edema or other process). As with most maxillofacial trauma, traumatic CSF leaks occur most com­monly in young males and complicate 2% of all head traumas, and 12–30% of all basilar skull fractures. Anterior skull base leaks are more common than middle or posterior leaks, due to the rm adherence of the dura to the anterior bas­ilar skull. The most common sites of CSF rhinor­rhea following accidental trauma are the sphenoid sinus (30%), frontal sinus (30%), and ethmoid/ cribriform (23%), When looking at surgical trauma, the most common sites of CSF leak fol­lowing FESS are ethmoid/cribriform (80%), fol­lowed the frontal sinus (8%) and sphenoid sinus (4%). After neurosurgical procedures, the most common site of CSF leak is the sphenoid sinus (67%) because of the high number of pituitary tumors that are addressed via transsphenoidal approach [17–19].

Overlay, underlay, combined, and the oblitera­tion techniques can be used for CSF closure. Overlay grafts are placed over the defect and these are outside the bony cranial cavity. The underlay grafts could be of two types (these are inside the bony cranial cavity). The epidural underlay graft is between the bone and the dura matter. The intradural underlay graft is placed in the subdural space. The combined techniques can be used. In a meta-analysis of the literature, both techniques yielded similar results. In the epidural underlay technique, the intact dura is separated from the edge of the skull base defect to expose an adequate buttress for the stabilization of the graft. The free graft should be designed in such a way that it can be pushed few millimeters between the bone and the dura on all the sides of the defect. Bone or cartilage underlay grafts are advocated for large bony defects associated with herniating brain or meninges. The inlay tech­nique is technically more demanding than the overlay technique. Inlay grafting is also suited to repair defects of the posterior wall of the frontal sinus, the cribriform plate, the ethmoid roof, and the sphenoid sinus in some cases. The onlay (overlay) technique is recommended if there is a risk of nerves or vessels injury. It is also indicated when an inlay technique is not technically possi­ble. The graft is placed generally over the dural lesion and over the exposed bony margins, which have been denuded of the mucosa. The graft is supported in place with layers of Gel foam/Gel lm or Surgicel; followed by a packing, overlay grafts (79%) are more frequently used as com­pared to inlay grafts (12%). As an alternative, a vascularized haddad ap (nasoseptal ap) can be used designed over the nasal septal branch of sphenopalatine artery (Fig.29.2a–c).