NEURO-SPECT EVALUATION OF CAROTID STENOSIS BEFORE AND AFTER ANGIOPLASTY AND STENTING

Article Nº AJ04-6

Brain SPECT is an examination that estimates regional cerebral blood flow (rCBF), which has great utility in the management of patients with cerebral ischemia. We present a case report of a patient that presents with a critical intracranial internal carotid stenosis caused by atheromatous plaque. The patient was evaluated with brain SPECT which demonstrated an excellent correlation of rCBF and the degree of carotid stenosis. Also, this examination was a reliable means of non-invasive imaging of carotid patency after angioplasty treatment of the stenosis.

A 72-year-old man with a history of diabetes mellitus type I, hypertension, coronary artery disease, multiple coronary artery by-pass, presents with 3 months of right pulsatile tinnitus, which has increased in intensity during the past 3 weeks. On physical examination, he has auscultable systolic thrill over the temporal and retro-mastoid regions of the skull. On neurological examination, he only has a mild decrease of cognitive function, without any other neurological deficits. The rest of the neurological exam is normal. A brain MRI exam is normal. A cerebral digital subtraction angiogram shows a critical stenosis > 90% of the right intracranial internal carotid artery, in the petrous segment. Also, there is poor filling of the right anterior cerebral artery and the middle cerebral artery (MCA), in particular the anterior division of the MCA (Figure 1a). The brain SPECT exam with Tc99m HMPAO shows a marked hypoperfusion of both anterior circulations (Figure 2). The hypoperfusion of the contralateral hemisphere can be explain as a steal phenomenon, since there is anterior cross filling from left to right via the anterior communicating artery.

Figure 1 (click= zoom)

Figure 2 (click=zoom)

The patient was greatly distressed by the constant noise of the tinnitus, which interfered with his sleep. Also he was preoccupied about the danger that the carotid stenosis itself could cause a cerebral infarct. He was therefore, resolute to be treated with angioplasty. He was well informed of the possible risks of an iatrogenic neurologic complication and consented for the procedure. He did not have any clinical signs of depression at the time of counseling.

A right 7F femoral approach was obtained. A 7F guiding catheter was advance to the right common carotid artery. After anticoagulating the patient with 8000 units of intravenous heparin, a Schneider Bonnie microballoon and a ACS, High Torch Floppy 0.014 microwire were navigated across the stenosis, and dilating the vessel to 2.5mm, leaving a residual stenosis of approximately 40% (Figure 1b) and marked improved filling of right sylvian branches. There were no angiographic complications. Immediately after the procedure, the patient reported that the tinnitus noise resolved. A control brain SPECT exam showed marked improvement of the hypoperfusion of both cerebral hemispheres, documented by a reduction of number of voxels with rCBF less than 50% than average (Figures 3 and 4).

Figure 3 (zoom=click)

Figure 4 (zoom=click)

The patient remained without tinnitus for three weeks, after which he began to once again hear a mild pulsatile noise in his right ear. On physical examination, he had an auscultable systolic thrill in the right temporal and retromastoid region. Due to a clinical suspicion of an early carotid re-stenosis post angioplasty, he had a new brain SPECT examination which showed worsening hypoperfusion of both anterior cerebral circulations (Figure 5). A new cerebral angiography showed re-stenosis in the same location of the carotid to approximately 70%. (Figure 1c). Therefore, it was decided to stent the stenotic lesion with a AVE gfx microstent of 3.0mm diameter (Figure 1d), and once again the tinnitus resolved. A control brain SPECT exam showed complete normalization of the rCBF of both anterior cerebral circulations. (Figure 6). The patient was discharged on aspirin indefinitely and Ticlid for four weeks.

The patient presented only with pulsatile tinnitus. The tinnitus was probably caused by turbulent blood flow caused by the stenotic lesion, which transmitted the noise through the skull base to the cochlea. The turbulent blood flow was completely corrected by the stent. There is only one reported case in the literature (1) about a patient who presents with tinnitus cured by stenting of an intrapetrous internal carotid stenosis. Fortunately, the patient had not experienced any neurologic deficit. Only a detailed psychometric examination found a mild cognitive deficit, mainly related to memory. Therefore, the indication for treatment of this lesion was the disruptive nature of the tinnitus noise and the fear that this critical carotid stenosis could cause a cerebral infarct. This was made even more apparent to the patient with the results of the first brain SPECT examination which showed marked bilateral cerebral anterior hypoperfusion.

The brain SPECT is an important diagnostic tool in the evaluation of the patient with cerebral ischemia. It is possible to distinguish between different etiologies of cerebral ischemia like embolic or hemodynamic decompensation by evaluating the distribution of the hypoperfusion (cortical sylvian versus watershed distribution respectively). Also important is the ability to estimate the area of ischemic penumbra by comparing the region of hypoperfusion below two standard deviations (SD) of the normal mean (superficial hypoperfusion) versus the region of hypoperfusion below more than four SD (deep hypoperfusion). This analysis of hypoperfusion is even more precise utilizing a quantitative analysis by comparing voxel by voxel the extension of hypoperfusion.

In this patient, the brain SPECT exams had a high correlation between the degree of hypoperfusion and the degree of carotid stenosis shown on the angiographic images. This type of evaluation of rCBF is also important in the evaluation of stenosis in other supra-aortic vessels such as the subclavian artery, the innominate artery and the vertebral arteries.

Lastly, the estimation of the rCBF in relation to a occlusive arterial disease provides important information for the clinician in the management of blood volume and blood pressure.

1. Emery DJ, Ferguson RD, Williams S. Pulsatile tinnitus cured by angioplasty and stenting of petrous carotid artery stenosis. Arch Otolaryngol Head Neck Surg. 1998;124:460-61.