Trauma Traumatic Injuries of the Skull Base

Region

Localisation

Region I

Anterior wall of the frontal sinus

Region II a

Lamina cribrosa

Region II b

Roof of the ethmoid bone

Region III a

Roof of the sphenoid sinus

Region III b

Lateral wall of the sphenoid sinus and adjacent petrous bone

Surgical revision is indicated for fractures of region I. The procedure for fractures of regions II a and II b depends on the size and number of defects. Smaller lesions can be treated endoscopically. In case of extended fractures, the authors recommend an open transcranial frontobasal revision. For regions III a and III b, an endoscopic procedure should be performed because of the difficulties when approaching these regions transcranially.

4.1.2 Clinical Signs and Symptoms

General clinical signs of a trauma of the anterior skull base are:

Skin contusions of the forehead
Haemorrhage from nose and/or throat
Deformities of the nose and forehead
«Racoon eyes» or unilateral orbital bruising
Hyposphagma (subconjunctival haemorrhage)

Further symptoms of involvement of the nasal sinuses are:

Rhinorrhoea
Meningitis (if CSF leak has not been treated)
Anosmia

In cases of involvement of the optic canal or the posterior orbit, additional symptoms occur due to lesions of the optic system:

Visual disorders or loss of vision (lesion of optic nerve )
Scotomas (lesion of optic nerve)
Double vision (lesions of oculomotor, trochlear or abducens nerve )
Mydriasis (lesions of oculomotor nerve )

In most cases frontobasal injuries do not cause any symptoms, especially during the first few hours or days after trauma. Therefore, the primary diagnosis is often made radiologically with a CT scan in the emergency room.

4.1.3 Investigations

Nowadays the initial trauma CT scan includes thin-sliced bone window image sequences in the axial and coronal planes. This enables the detection of thin fracture lines and intracranial air bubbles as signs of injury to the anterior skull base.

If there are clinical signs of a CSF leak from the nose, it is necessary to verify the beta trace protein in the fluid in question. This protein is a prostaglandin D synthase of which the concentration in CSF is 35 times higher than in serum [8].

In cases of a secondary CSF leak of unclear location of the origin, it might be helpful to perform an MRI scan in the prone position. During this examination, it is possible to detect fluid collections in the paranasal sinuses or the presence of CSF flow on T2 weighted image sequences.

If CT and MRI scans are not successful in detecting the location of the CSF leak, then the fluorescein technique is a very sensitive method for detecting a CSF fistula into the nasal sinuses [15]. This method uses a solution of 5% sodium fluorescein which is applied through a lumbar spinal tap. Following this, a nasendoscope with a blue filtered light source and a complementary blocking filter is used. Using this method even the smallest traces of fluorescein-stained CSF can be detected [15].

4.1.4 Therapeutic Options

Injuries of the anterior skull base bare the specific risk of a CSF leak into the frontal, ethmoid or sphenoid sinuses which may develop into secondary meningitis. Therefore, surgical intervention should be considered in most cases of persisting CSF leak. In cases of no CSF leak or CSF rhinorrhoea that resolves spontaneously within days, these injuries may be managed conservatively. Uncomplicated fractures of the orbital roof do not require surgical therapy. Orbital fracture reduction is required in significant dislocation of bony fragments into the orbit in the presence of symptomatic diplopia.

If there is evidence of dislocation of bony fragments into the optic canal with signs of impaired visual function, then an emergency surgical decompression of the optic nerve is indicated because of the risk to vision.

The surgical method depends on the extension and the location of the fracture. Small lesions with intact sense of smelling are treated minimally/invasively using endonasal endoscopy by an ENT surgeon [1, 4–6]. Lesions of the very dorsally located sphenoid sinus should be treated endoscopically because a transcranial approach bears a relatively high risk of surgical morbidity. Fractures of the orbits especially with concomitant fractures of the midface are treated by maxillofacial surgeons.

In cases of extensive defects of the anterior skull base in region II a and II b (see above) with persisting CSF leak, the classical neurosurgical technique of transcranial frontobasal revision using a subfrontal approach is indicated (◘ Figs. 4.1, 4.2, 4.3, and 4.4) [2, 12]. This technique enables a safe and watertight covering of the anterior skull base with a pericranial flap. When using this method, it is by its natures impossible to preserve sense of smell. Therefore, it should only be indicated in cases of previous traumatic anosmia. For a detailed description of the surgical technique, see ► Sect. 4.1.5.

Fig. 4.1

Left paramedian frontobasal fracture in the region of the Crista galli with clinical signs of rhinorrhoea following frontal a–c and frontobasal d–f traumatic injuries. CT scan (bone window) in axial a–d, coronal e and sagittal f planes

Fig. 4.2

Scheme of the operative strategy with coverage of the anterior skull base with fascia lata (red) and titanium mesh (blue) that presses the duraplasty onto the orbital roofs. The frontobasal dura itself is covered with Tachosil^TM (not shown in this image)

Fig. 4.3

Postoperative result of the patient from ◘ Figs. 4.1 and 4.2. Reconstruction of the anterior skull base and the frontal convexity with titanium mesh. Coronal a–c and axial d–f CT scans (bone window)

Fig. 4.4

Postoperative result of the patient from ◘ Figs. 4.1, 4.2, and 4.3. Reconstruction of the anterior skull base and the frontal convexity with titanium mesh. 3D volume rendering from CT data set

For smaller open head injuries involving the frontal sinuses, it is possible to use a direct surgical approach (◘ Figs. 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, and 4.12).

Fig. 4.5

Depressed frontal fracture a and frontobasal fracture with involvement of the anterior and posterior wall of the frontal sinus b following a motor vehicle accident. Bone window CT scan

Fig. 4.6

Patient from ◘ Fig. 4.5. Postoperative CT scan showing the reconstruction of the convexity of the skull a and of the frontal sinus b. Bone window CT scan

Fig. 4.7

Patient from ◘ Figs. 4.5 and 4.6. Intraoperative photograph demonstrating reconstruction of the convexity and the frontal sinus. The fragment of the frontal sinus’ posterior wall could be refixed. The multiple fragments of the anterior wall had to be replaced by titanium mesh

Fig. 4.8

Frontobasal injury including fractures of orbital roof, anterior and posterior wall of the frontal sinus as well as of the midface following a bicycle accident. There are intracranial air bubbles as a sign of skull base injury. 3D volume rendering and CT scan in three planes (bone window)

Fig. 4.9

Patient from the previous figure. Status after frontolateral craniotomy with duraplasty and osteosynthetic reconstruction of the frontobasal and midface fractures. 3D volume rendering and CT scan in three planes (bone window)

Fig. 4.10

Complex frontobasal injury after a drop from 2 m height with multiple fractures of both orbits a, b, the frontal sinuses c and the frontal convexity of the skull with a left-sided frontolateral epidural haematoma d. CT scan with bone window a, b, c and brain window d

Fig. 4.11

Patient from previous figure. Intraoperative photograph before a and after b osteosynthetic reconstruction of the complex frontobasal injuries and evacuation of the epidural haematoma. Reconstruction of the frontal convexity with mini-plates and of the anterior wall of the frontal sinus with titanium mesh b

Fig. 4.12

Patient from ◘ Figs. 4.11 and 4.12. Postoperative result after reconstruction of the anterior and posterior walls of the frontal sinuses a and the frontal convexity b. CT scan with bone window a and 3D volume rendering b

4.1.5 Surgical Technique of Frontobasal Duraplasty and Cranioplasty

The surgical technique of frontobasal duraplasty is suited for reconstruction of the anterior skull base for traumatic injuries as well as following extensive tumour resections. After a bicoronal skin incision, the galea has to be dissected, reverted inferiorly and fixed with self-retracting hooks. The periosteum and the connective tissue of the aponeurosis of the skull are initially left in place and then dissected from the bone during the next step. This kind of dissection creates a so-called pericranial flap that has the capacity to cover the whole anterior skull base if necessary (◘ Figs. 4.13, 4.14, 4.15, 4.16, and 4.17).

Fig. 4.13

Bifrontal skin incision with the use of LeRoy clips for haemostasis

Fig. 4.14

Retraction of the galea and dissection of the pericranial flap with the monopolar

Fig. 4.15

Final dissection of the pericranial flap in the supraorbital region

Fig. 4.16

Dissection of the periosteum from the skull

Fig. 4.17

Retraction of the pericranial flap with self-retracting hooks. A supraorbital fracture line can be seen on the right side

Usually a single frontal burr hole in the midline just over the superior sagittal sinus is sufficient to perform a bifrontal craniotomy . By using this burr hole, it is then necessary to carefully dissect the dura from the internal table to avoid dural injury or heavy epidural bleeding from an opened superior sagittal sinus during the craniotomy (◘ Figs. 4.18, 4.19, 4.20, 4.21, 4.22, and 4.23).