Balloon Test Occlusions

24 Balloon Test Occlusions

Arun P. Amar, Parampreet Singh, and Phillip Bonney

Abstract

Carotid artery sacrifice is a necessary adjunct in the treatment of a variety of vascular lesions as well as head and neck malignancies. Balloon test occlusion (BTO) is an important test to assess risk of ischemic complication following carotid sacrifice. In this chapter, we will discuss the indications, techniques, and complications associated with BTO.

Keywords: balloon test occlusion, angiogram, endovascular, SPECT, carotid

24.1 Goals

1. Understand the indications for balloon test occlusion (BTO).

2. Analyze standard techniques for BTO.

3. Evaluate the nuances and complications associated with this procedure.

4. Review adjunct modalities aimed at improving prediction of ischemic complications with BTO.

24.2 Case Example 1

24.2.1History of Present Illness

A 62-year-old, right-handed woman presented with a 1-year history of persistent right-sided ear discharge. Imaging revealed a mass involving the right external auditory canal extending to the petrous bone with involvement of the petrous segment of the right internal carotid artery (ICA). A biopsy confirmed squamous cell carcinoma. The patient was scheduled to undergo a resection of the tumor with possible right ICA sacrifice.

Past medical history: Hypothyroidism, hyperlipidemia, colon cancer.

Past surgical history: Partial colectomy for colorectal carcinoma.

Family history: Noncontributory.

Social history: Noncontributory.

Review of systems: As per the above.

Neurological examination: Unremarkable.

Imaging studies: Right external auditory canal mass with provided history of squamous cell carcinoma. There is extension into the middle ear cavity, right condylar fossa and destruction of the anterior petrous portion of the temporal bone (▶ Fig. 24.1a).

24.2.2 Treatment Plan

Given the possibility of potential sacrifice of the right ICA during surgery, the patient underwent a preoperative BTO with hypotensive challenge followed by HMPAO SPECT (hexamethylpropy-leneamine oxime single-photon emission computed tomography). The study was negative clinically, angiographically, and on SPECT scan (▶ Fig. 24.1).

24.2.3 Follow-up

Following BTO, the patient underwent a successful resection of her tumor without requiring carotid sacrifice.

24.3 Case Example 2

24.3.1History of Present Illness

A 63-year-old, right-handed woman was referred by her primary physician after imaging for headache work-up revealed a 2-cm left ICA cavernous aneurysm with intradural extension. The patient was referred for a BTO prior to therapeutic ICA occlusion for treatment of this partially thrombosed giant aneurysm.

Past medical history: Hypertension, hyperlipidemia, obesity.

Past surgical history: None.

Family history: Negative for aneurysms or subarachnoid hemorrhage.

Social history: Noncontributory.

Review of systems: As per the above.

Neurological examination: Unremarkable.

Imaging studies: Computed tomography angiography (CTA) showed a large, partially thrombosed, left ICA cavernous segment aneurysm (▶ Fig. 24.2a).

24.3.2 Treatment Plan

Given the size, morphology, and partial thrombosis of the aneurysm, both endovascular embolization and open clip ligation were deemed high risk. Permanent occlusion of the carotid was therefore planned. A BTO with HMPAO SPECT study was performed to evaluate the safety of left carotid occlusion. The study was negative clinically and angiographically; however, on HMPAO SPECT imaging subtle asymmetry was noted, suggestive of hypoperfusion rendering an overall intermediate risk status.

24.3.3 Follow-up

Following the BTO, the patient underwent a successful surgical ligation of the left cervical ICA, and an intracranial superficial temporal artery to middle cerebral artery (STA-MCA) bypass was performed due to the findings of the HMPAO SPECT scan (▶ Fig. 24.2). There were no ischemic complications.

24.4 Case Example 3

24.4.1History of Present Illness

A 68-year-old, right-handed man presented with progressive left-sided hearing loss and facial weakness. Imaging revealed a mass involving the left temporal bone and ear canals. Biopsy confirmed a squamous cell carcinoma, and the patient was planned to undergo a temporal bone resection with parotidectomy and possible left ICA sacrifice.

Fig. 24.1(a) Magnetic resonance angiography (MRA) with right external auditory canal (EAC) mass involving the right petrous bone in close proximity to the right internal carotid artery (ICA). (b) Balloon microcatheter inflated in the right petrous ICA. (c) Contralateral ICA run with balloon microcatheter inflated in the right petrous ICA with minimal filling across the anterior communicating artery, (d) Posterior circulation run with balloon microcatheter inflated in the right petrous ICA, with robust filling of the left internal carotid via a posterior communicating artery, (e) Follow-up HMPAO SPECT (hexamethylpropyleneamine oxime single-photon emission computed tomography) shows symmetric filling of the bilateral hemispheres. (Representative imaging for both cases 1 and 3.)

Past medical history: Hypertension, hyperlipidemia, hypothyroidism.

Past surgical history: None.

Family history: Noncontributory.

Social history: Noncontributory.

Review of systems: As per the above.

Neurological examination: Left-sided sensorineural hearing loss and subtle left nasolabial flattening (House-Brackmann scale 2). The remainder of the neurological examination was unremarkable.

Imaging studies: Mass associated with the left external auditory canal, middle ear cavity, and mastoid temporal bone with superior extension into the middle cranial fossa, as well as anterior-inferior extension into the temporomandibular joint (▶ Fig. 24.3a).

24.4.2 Treatment Plan

Given the possible need for intraoperative left ICA sacrifice, the patient underwent BTO of the left ICA with hypotensive challenge and HMPAO SPECT study. The study was negative clinically, angiographically, and on SPECT scan (▶ Fig. 24.3).

24.4.3 Follow-up

Following the BTO, the patient underwent a successful resection of his tumor without requiring carotid sacrifice.

24.5 Level of Evidence

BTO is an important test for prediction of ischemic complications following a permanent carotid occlusion.

The sensitivity of BTO is increased with addition of adjunctive modalities such as hypotensive challenge, HMPAO SPECT, positron emission tomography (PET), magnetic resonance imaging (MRI), and transcranial Doppler (TCD), among others. Majority of evidence for these procedures are based on observational case series and expert opinion only (Level of Evidence C).

24.6 Case Summaries

1. What is the purpose of BTO?

Elective carotid sacrifice is necessary in certain clinical settings involving resection of head and neck tumors and in complex vascular lesions, such as fistulas or large aneurysms.

Fig. 24.2 (a) Left internal carotid artery (ICA) cavernous segment aneurysm (> 2 cm) with intradural extension, (b) A balloon microcatheter inflated in the petrous left ICA. (c) Right ICA angiogram with occluded left ICA (petrous segment, white arrow). No significant cross-filling noted, (d) Posterior circulation angiogram with balloon inflated in the petrous left ICA, demonstrating robust filling of the left ICA via a posterior communicating artery. (e) Subtle asymmetry noted in the HMPAO SPECT (hexamethylpropyleneamine oxime single-photon emission computed tomography) scan predominantly in the left frontoparietal regions (white arrows) following completion of the balloon test occlusion (BTO).

ICA ligations are associated with ischemic complications in 49% of patients. Similarly, in common carotid artery occlusions, ischemic complications were noted in 28% of patients ¹^,²^,³ with a mortality of about 12%.⁴ These complications may arise due to poor collateral circulation across the circle of Willis, inadequate reserve despite good collateral flow, and thromboembolism. However, with favorable anatomy, vessel sacrifice can be asymptomatic. BTO is an endo-vascular angiographic procedure which simulates an arterial occlusion in a controlled environment to predict ischemic complications.

2. What are the procedural complications and associated prevention strategies associated with BTO?

The major complications associated with BTOs may be asymptomatic or symptomatic vessel injury and/or transient or persistent ischemic events. The largest BTO case series to date by the University of Pittsburgh reported asymptomatic events in 1.6% of patients and symptomatic events in 1.6% (1.2% transient and 0.4% permanent).⁵ Similar results have been reported by others which are within the range for diagnostic angiography alone.⁶^,⁷ The major preventative strategies include correct sizing of the balloon and preinflation heparinization.

3. What adjunctive modalities are used with BTO to increase sensitivity and specificity?

The common adjunctive modalities to improve predictions of ischemic complications include clinical testing with a simulated hypotensive challenge, TCD ultrasonography, Xenon-enhanced computed tomography, 0-15 labeled PET, or 99mTc-HMPAO SPECT. The literature on these techniques is discussed below.

4. What are the common causes of ischemic complications and preventative strategies following permanent occlusions in patients with a negative BTO?

Fig. 24.3 (a) Magnetic resonance imaging (MRI) T1 with contrast showing left temporal bone mass in close proximity to the left petrous internal carotid artery (ICA) (arrow), (b) A high-grade stenosis in the left ICA origin which poses technical difficulties and risk of embolizing the plaque intracranially during passage of a balloon microcatheter. A dual balloon setup is employed as seen in the next image, (c) Dual balloon setup with a balloon guide catheter (8F Stryker Flowgate) inflated in the left common carotid artery, and a balloon microcatheter (4-mm Scepter XC) inflated in the right external carotid artery with stagnant flow in the left ICA. (d) Contralateral ICA angiogram demonstrating delayed arterial cross-filling on the left through the anterior communicating artery, (e) A posterior circulation angiogram demonstrating good filling in the arterial phase via a robust posterior communicating artery.

Following a negative BTO, there is still a 4.7 to 25% risk of ischemic complications, depending upon the adjunct modal-ity_4,5,8,9,io The major causes of these ischemic complications include both hemodynamic insufficiency and thromboembolism. A rescue bypass has been utilized to correct hemodynamic complications with success.¹¹^,¹² Short-term anticoagulation or antiplatelet therapy can be considered following permanent occlusions to reduce risk of stump embolism.¹³ There are, however, no evidence-based guidelines for these strategies.

24.7 Landmark Papers

Serbinenko FA. Balloon catheterization and occlusion of major cerebral vessels. J Neurosurg 1974;41(2):125-145.

Prior to the introduction of formal BTO,¹⁴ methods to determine the functional adequacy of the circle of Willis involved indirect cerebral blood flow (CBF) measurements such as angiography with manual compression, ICA stump pressure measurements, and oculoplethysmography (OPG).¹⁵

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