An Imaging Review of Postoperative Complications of Skull Base Surgery

Dr Rekha Siripurapu, Dr Amit V HerwadkarSalford Royal NHS Trust Greater Manchester Neurosciences UnitManchester, UK

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Purpose

To review the imaging features of complications following skull base surgery

Approach

Imaging appearances of various complications of skull base surgery will be discussed

This review includes complications following traditional neurosurgical as well as minimally invasive endoscopic techniques

Discussion

Skull base surgery has evolved Newer techniques More complex conditions which

previously were not treated

Complications Integral to a surgical procedure

Role of imaging

1. Identify the “at risk”

2. Evaluate the complications post operative

1. Perioperative 2. Sub acute 3. Delayed

Post operative complications

Post operative complications

Perioperative

Subacute Delayed

1. Vascular injury

2. Neural injury

3. CSF leak

1. CSF leak2. Infections3. Venous

sinus thrombosis

4. Migration of bone wax or fat packing

1. Meningoencephalocele

2. Loculated posterior fossa collections

3. Delayed infection

Perioperative Complications

Post contrast axial (a) and coronal (b) MR images show a giant right sphenoid wing meningioma completely encasing and narrowing the right ICA (arrow in a ), displacing and encasing the right MCA (arrow in b). Catheter angiogram shows tumour blush and confirms the ICA encasement and displacement with prominent perforators from the MCA (double arrow).

a cb

Giant Sphenoid Wing Meningioma

Vascular injury : Perforator vessel Traditional right pterional approach

Intraoperative MCA perforator bleeder was clipped to secure haemostasis

The VR image from CTA done immediate post operative shows a clip at the superior aspect of the right MCA, M1 . The M1 proximal to the clip is narrow (arrow). The vessel distal to the clip is patent.Note the narrowed supraclinoid ICA ( double arrows) as it courses through the tumour.

Day 1 post tumour resection and clipping developed left weakness

Non contrast CT shows acute infarct involving basal ganglia and frontal lobe

Catheter angiogram shows clip at the superior aspect of MCA (arrow), patent narrow M1 but occluded right M2 branches ( double arrows).

Vascular injury : Perforator vessel Traditional right pterional approach

Vascular injury: ICA LacerationEndoscopic trans sphenoidal approach for pituitary microadenoma

Selective Catheter angiography following endoscopic trans sphenoidal surgery complication of laceration to the right internal carotid artery (ICA). a. Right ICA run demonstrates extravasation of contrast from ICA ( arrow). b and c. ICA vessel sacrifice to treat the injury

a b c

Pituitary macroadenoma

Coronal T2 (a), sagittal T1(b) and post contrast coronal T1(c ) show a giant pituitary macroadenoma with evidence of haemorrhage superiorly (*). The anterior cerebral arteries are displaced superiorly and closely related to the tumour ( arrow).

a b c

Vascular injury: Traditional anterior skull base approach

Intraoperatively , several tumour vessels noted to be arising from the anterior cerebral arteries at the dome and slowly dissected from the dome. In doing this arterial bleed encountered from the right A1/A2 junction, which could not be diathermied and haemostasis eventually achieved with some difficulty by using muscle/surgicel wrap

Non contrast CT shows anterior intehemispheric hematoma . Also note infarction involving the right caudate head and anterior lentiform ( arrow) , in the territory of recurrent artery of Heubner.

Vascular injury: PseudoaneurysmTraditional anterior skull base approach

Catheter angiogram images show a pseudo aneurysm at the right A1/A2 junction ( arrow).

Vestibular Schwannoma

Axial FIESTA , post contrast axial and coronal T1 show a large right vestibular Schwannoma extending from the IAM into the CP angle cistern ad slightly indenting the brain stem without significant distortion.

a b c

Subarachnoid haemorrhage and infarct Translabyrinthine approach

Right sided translabyrinthine approach with fat packing of the mastoid cavity ( asterisk) ; no intraoperative note of complications.Non contrast CT images, immediate post operative, show increased density (arrow) in the prepontine cistern and interpeduncular cistern consistent with acute subarachnoid haemorrhage. Note the early dilatation of temporal horns . Also note low density in the right cerebellum suggestive of infarction ( double arrows).

Patient slow to recover from GA and woke up with left sided weakness.

Arterial infarction & Venous thrombosis Translabyrinthine approach

a b c

Corresponding to the CT low density , Axial T2 (a) shows high signal intensity in the right middle cerebellar peduncle extending into cerebellum . DWI - B1000 (b) shows high signal with corresponding low ADC (c ) consistent with an infarct. Note the right translabyrinthine approach with fat packing of mastoid cavity ( asterisk). Also note the abnormal signal of the right transverse sinus ( double arrow) suggestive of venous sinus thrombosis on day 2 MRI.

a b c

Post contrast axial T1 (a) and coronal T1 (b) show a very large enhancing anterior cranial fossa mass extending into adjacent bone, para nasal sinuses and to the subcutaneous tissues . Histology confirmed a grade 2 meningioma. CT( c) shows lucency as well as hyperostosis of the frontal bone (arrow).

Anterior cranial fossa and craniofacial grade 2 meningioma

Vascular injury: Lobar hematomaExtended anterior cranial fossa and craniofacial approach

Non contrast CT shows large left frontal hematoma with subdural and subarachnoid extension of haemorrhage.

Vascular injury

Detailed pre operative vascular imaging such a CT / MR angiography is important to ascertain the anatomy

Meticulous haemostasis is crucial

Arterial bleeding from small intracranial vessels is challenging as sacrifice of the vessel may result in ischemia

Injury to the internal carotid artery is rare. Can lead to massive arterial bleeding and pseudoaneurysm or carotid-cavernous fistula formation

Singh A et al. Operative Techniques in Otolaryngology (2011) 22, 237-245

CSF leak: Chiari MalformationForamen magnum decompression

Sagittal T2 (a) and T1 (b) show a large CSF signal collection extending from the posterior fossa into the subcutaneous tissues in keeping with a pseudomeningocoele following foramen magnum decompression for a Chiari malformation.

a b

Subacute Complications

Clival Chordoma

Axial T2 ( a) and sagittal T1 (b) images show a well defined lesion within the clivus ( arrow) which is high signal intensity on T2 , Typical of a chordoma and is low intensity on T1. The lesion did not enhance ( not included). CT shows expansile lucency with some residual trabeculae but no calcification. Histology confirmed chordoma.

a b c

CSF Leak and meningitis:Extended Endoscopic trans sphenoidal resection and mesh repair

CT cisternogram shows a defect in the clivus at its middle third which has been has been plugged with Dura foam and refashioned with the mesh (small arrow). A small amount of contrast leaks through this defect deep to the mesh ( long arrow)

CSF Leak and meningitis:Extended Endoscopic trans sphenoidal resection and mesh repair

The MR cisternogram demonstrates contrast opacification of the sphenoid sinus(arrow) confirming CSF leak.The dural defect was repaired using Subcutaneous fat harvested from peri-umbilical wound , then covered with spongostan and Durafoam. This was held together by the titanium mesh that was secured at the top end with a 5mm screw .

CSF leak Common complication: risk of pneumocephalus and

meningitis The introduction of closure techniques for extended

skull base defects such as the vascularized nasoseptal flap etc. have reduced overall postoperative CSF leak rates to well below 5%

Most postoperative CSF leaks are diagnosed clinically

Imaging findings include large volume pneumocephalus , increasing pneumocephalus, pseudomeningocoele and intracranial hypotension

Site of leak can be identified by CT / MR cisternogramSingh A et al. Operative Techniques in Otolaryngology (2011) 22, 237-245

Vestibular Schwannoma

Axial FIESTA , post contrast axial and coronal T1 show a large right vestibular Schwannoma extending from the IAM into the CP angle cistern ad slightly indenting the brain stem without significant distortion.

a b c

Venous sinus thrombosisTranslabyrinthine approach

CT Venogram shows filling defect within the right transverse sinus ( arrow), non opacification of the distal transverse and sigmoid sinuses (double arrow) consistent with venous sinus thrombosis. Collateral drainage via the tentorial veins ( black arrow) and right vein of Labbe .

Venous sinus thrombosis

Recognised complication following skull base surgery

Can be seen with both translabyrinthine and retrosigmoid approaches

In translabyrithine approach, thought to occur due to wide exposure and manipulation of the venous sinuses

1. Daniel Thomas Ginat , Gul Moonis , and Suresh K. Mukherji . Imaging of the Postoperative Skull Base and Cerebellopontine Angle . Atlas of post surgical neuroradiology. 10.1007/978-3-642-15828-5_6

2. Madjid  S amii and Venelin Gerganov. Approaches to cerebello pontine angle. Surgery of Cerebellopontine Lesions. 10.1007/978-3-642-35422-9_4

Epidermoid

a b c

d

MR shows a T2 (a) high signal intensity, non enhancing (b) right CP angle cistern lesion indenting the middle cerebellar peduncle. The lesion is high signal intensity on B1000 ( c) and low on ADC (d) in keeping with restricted diffusivity, characteristic of Epidermoid cyst.

Migration of bone wax and venous sinus thrombosis Retrosigmoid approach

Developed headaches post right retrosigmoid approach and epidermoid clearance

Non contrast CT demonstrates a low density abnormality in the right sigmoid sinus measuring -30 HU ( fat attenuation) . Please note the retrosigmoid craniectomy with low density bone wax (arrow) at the margins of the craniectomy defect. Increased density of the sinus is noted ( 71 HU) raising the possibility of venous sinus thrombosis.

Migration of bone wax and venous sinus thrombosis Retrosigmoid approach

Intraoperative sigmoid sinus bleed which was controlled with bone wax

Non contrast CT demonstrates a low density abnormality in the right sigmoid sinus measuring -30 HU ( fat attenuation) . Please note the retrosigmoid craniectomy with low density bone wax (arrow) at the margins of the craniectomy defect. Increased density of the sinus is noted ( 71 HU) raising the possibility of venous sinus thrombosis.

Migration of bone wax and venous sinus thrombosis Retrosigmoid approach

CT Venogram confirms non opacification of the dominant right transverse and sigmoid sinuses and right IJV consistent with venous sinus thrombosis (arrow) . Note the extension of bone wax from craniectomy margin into the sigmoid sinus and IJV ( yellow arrow) and consequent venous thrombosis.

CT Venogram images show low density filling defect (arrow) in the sigmoid sinus extending into the jugular bulb following retrosigmoid approach to posterior fossa craniotomy. The attenuation of the filling defect was that of fat, in keeping with migrated bone wax. Of note, there was brisk venous bleeding at the margins of the craniotomy which was controlled with bone wax.

Migration of bone wax: case 2 Retrosigmoid craniotomy

Migration of bone wax Bone wax used to control the venous bleeding from the

margins of craniectomy

Bone wax is stable in body and usually not associated with complications

Can rarely migrate into the sigmoid sinus via an emissary vein

Hadeishi et al described this is in 7 cases, of which two had venous sinus thrombosis . They suggested that intrasurgical application of a large quantity of bone wax to control the bleeding from the large emissary veins carries a risk of bone wax migration into the sigmoid sinus

Hadeishi H, Yasui N, Suzuki A. Mastoid canal and migrated bone wax in the sigmoid sinus: technical report. Neurosurgery 1995; 36:1220–1223.

Delayed Complications

PseudomeningocoeleTranslabyrinthine approach

Right sided CSF signal intensity collection (arrow) in keeping with a pseudomeningocoele following a right sided trans labyrinthine approach to resection of a vestibular Schwannoma. Note the interesting extension of the meningocele via the jugular foramen into in carotid space ( double arrows) .

Meningoencephalocele Combined approach for cholesteatoma removal

Axial T2 images show a right sided mastoid post surgical changes and a Meningoencephalocele (arrow) extending into the right mastoid cavity. Note the herniation of posterior right temporal cortex ( double arrow) .

a b c

Post contrast axial T1 (a) and coronal T1 (b) show a very large enhancing anterior cranial fossa mass extending into adjacent bone, para nasal sinuses and to the subcutaneous tissues . Histology confirmed a grade 2 meningioma. CT( c) shows lucency as well as hyperostosis of the frontal bone (arrow).

Anterior cranial fossa and craniofacial grade 2 meningioma

Subdural empyema 3 months laterExtended anterior cranial fossa and craniofacial approach

Post contrast T1 images demonstrate a peripherally enhancing extra axial collection in keeping with a subdural empyema (short arrow) along with extension into the brain parenchyma ( long arrow). Also note a non enhancing right parafalcine collection ( white arrow).

Frontal meningoencephalocele

ba

Coronal CT reformat (a) image shows a large defect in the cribriform plate ( arrow). Coronal T2 MR (b) image demonstrates a meningoencephalocele extending into the left nasal passage.

Brain abscess 1 month laterAnterior cranial fossa approach

a b c

e

d

MRI demonstrates rim enhancing ( b and c) left frontal lobe lesion with significant surrounding oedema on axial T2 (a). The non enhancing component of the lesion demonstrates high signal on B1000 (d) and low ADC (e) (arrow) in keeping with restricted diffusivity that is typical of an abscess.

Infection

Infection acquired after anterior cranial resection is predisposed by concurrent partial anterior frontal lobectomy, prior craniotomy, and high doses of radiotherapy.

Alloplastic materials used for reconstruction and

devitalized tissues are also risk factors.

Intracranial infections are often in the midline, perhaps due to the proximity to the parasanal sinuses.

Daniel Thomas Ginat , Gul Moonis , and Suresh K. Mukherji . . Imaging of the Postoperative Skull Base and Cerebellopontine Angle . Atlas of post surgical neuroradiology. 10.1007/978-3-642-15828-5_6

Conclusion

Imaging plays a very important role in the assessment of post operative skull base

Factors influencing type of complications pre operative “at risk” structuresSurgical approach used

CT and MRI are complimentary in assessing the complications

Vascular imaging is essential for evaluation of vascular injury

Acknowledgments

Neurosurgery and Neuroradiology colleagues Manchester Skull Base UnitManchester, UK

Thank you

Any questions or suggestions , please email rekhasiripurapu@gmail.com