2025 年 12 巻 p. 349-354
Spontaneous internal carotid artery dissection is a rare condition that generally affects middle-aged individuals. Most cases of reported spontaneous internal carotid artery dissections are unilateral, but approximately 10%-20% involve bilateral internal carotid arteries. Spontaneous internal carotid artery dissection generally presents with neck pain, ischemic cerebral symptoms, and/or Horner's syndrome. Pulsatile tinnitus is present in around 5%-10% of spontaneous internal carotid artery dissection cases. However, this is generally accompanied by other major internal carotid artery dissection symptoms. Herein, we report a case of bilateral spontaneous internal carotid artery dissection that presented with unilateral pulsatile tinnitus of sudden onset as an isolated symptom. An otherwise healthy 50-year-old man visited a neurosurgical clinic complaining of right temporal pulsatile tinnitus that had begun 1 day prior. In addition to tinnitus, a thorough symptom interview revealed mild heavy-headedness. Magnetic resonance angiography showed bilateral extracranial internal carotid artery dissections and severe stenosis of the true lumen of the right internal carotid artery. No cerebral ischemic lesions were observed. Administration of 5 mg/day amlodipine and 100 mg/day aspirin was initiated. Following the 9th day after onset, the pulsatile tinnitus gradually improved. Around the 40th day after onset, the pulsatile tinnitus disappeared, and magnetic resonance angiography showed an improvement of the right internal carotid artery stenosis. Magnetic resonance angiographies at 5 and 9 months after onset revealed complete disappearance of the false lumen and slight stenosis of the right internal carotid artery at the entrance of the carotid canal. This case suggests that the sudden onset of isolated unilateral pulsatile tinnitus can be a clue to the diagnosis of spontaneous internal carotid artery dissection.
Spontaneous internal carotid artery dissection (ICAD) is a rare condition with an annual incidence of 2.5-3.0 per 100,000,1-3) in which ICAD occurs without any particular risk factors, such as cervical trauma, connective tissue disease, or infectious disease etc..2,4-6) ICAD predominantly affects individuals aged 35-50 years, peaking in the fifth decade.2,7) Recently, easier access to magnetic resonance imaging (MRI) has led to more frequent discovery of spontaneous ICAD.6,8,9) Most reported cases of spontaneous ICADs are unilateral, but approximately 10%-20% involve the bilateral internal carotid arteries (ICAs).3,10-13) Spontaneous ICAD commonly presents with ischemic stroke, headache, partial Horner's syndrome, and/or neck pain.2,5,6) Although 5%-15% of ICAD patients present with pulsatile tinnitus, it is generally accompanied by the aforementioned common symptoms.14-17) Herein, we report a case of bilateral spontaneous ICAD that presented with the sudden onset of unilateral pulsatile tinnitus as an isolated symptom.
An otherwise healthy 50-year-old man, employed as a store clerk, visited a nearby neurosurgery clinic with a complaint of the right temporal pulsatile buzzing tinnitus, which had begun 1 day prior. He had no medical history of risk factors for atherosclerosis such as hypertension, hyperlipidemia, or diabetes mellitus. He has no prior history of head or neck trauma, severe neck torsion, connective tissue disorders, or head or neck infections. Physical examination revealed no neurological symptoms other than tinnitus. A thorough symptom interview revealed a mild-headedness. No objective bruits were heard during auscultation. Hearing was intact. MRI on the day of the visit revealed no abnormalities such as ischemic lesions in the brain or intracranial lesions causing tinnitus. However, magnetic resonance angiography (MRA) revealed dissection of the bilateral extracranial ICAs and false lumens from the bifurcations to the entrance of the carotid canals (Fig. 1A-E). It also revealed irregular narrowing of the true lumen of the right ICA, which was narrowest at the entrances of the carotid canal (Fig. 1A, B, and D). Other cervical arteries, including the common carotid and vertebral arteries, remained intact (Fig. 1C). T1 black-blood (T1BB) MRI depicted the false lumens as hyperintense areas around the true lumens (Fig. 1E). Arterial spin labeling (ASL) imaging with a 1.5-sec post-labeling delay showed a mild reduction in blood flow in the right temporal lobe (Fig. 1F). Three-dimensional digital subtraction angiography, performed 4 days after the onset, confirmed irregular narrowing of the right ICA and aneurysmal dilatation of the left ICA at the entrance of the carotid canal (Fig. 2). Whole-body computed tomography did not reveal any vascular abnormalities, such as aortic dissection or aneurysms. Further, routine blood tests, including those for inflammatory markers, were negative.
Magnetic resonance angiography (MRA) and arterial spin labeling (ASL) imaging were performed 1 day after right tinnitus onset.
MRA shows false lumens adjacent to the true lumens of the bilateral internal carotid arteries (ICAs) (asterisks in A, B, C, D, E).
Three-dimensional volume-rendering MRA clearly shows the extent of the false lumens (asterisks in D, colored in green). Coronal T1 black-blood MR imaging showing the false lumens as hyperintense lesions (asterisks in E) around the hypointense true lumens (arrows in E). Irregular narrowing of the right internal carotid artery was observed (arrows in A, B, D, E), which was narrowest at the entrance of the carotid canal (arrowhead in A, C, D). ASL with a 1.5-sec post-labeling delay showed a moderately decreased flow in the right temporal lobe (box in F).
Three-dimensional digital subtraction angiography (3D-DSA), performed 4 days after the tinnitus onset, demonstrated irregular narrowing of the right ICA (arrows in A), which was narrowest at the entrance of the carotid canal (arrowhead in A). It also showed aneurysmal dilatation in the left ICA at the entrance of the carotid canal (# in B).
ICA: internal carotid artery
The patient was diagnosed with spontaneous bilateral ICAD and was prescribed amlodipine 5 mg/day and aspirin 100 mg/day to prevent the progression of dissection and ischemic stroke. On the 9th day after the onset, his tinnitus started to gradually improve. Approximately 40 days after onset, the pulsatile tinnitus disappeared, and MRA showed an improvement in the right ICA stenosis.
MRA examinations at 5 and 9 months after onset revealed complete disappearance of the false lumen and normalization of the right ICA diameter, except for mild stenosis at the entrance of the carotid canal (Fig. 3A-C). It also revealed the disappearance of the aneurysmal dilatation of the left ICA. ASL imaging revealed the disappearance of the low-flow area in the right temporal lobe (Fig. 3D).
MRA and ASL at 9 months post-onset. The false lumens completely disappeared (A, B, C). Narrowing of the right ICA also disappeared, except for the mild and local stenosis at the entrance of the carotid canal (arrow in A, B, C). ASL with a 1.5-sec post-labeling delay showed disappearance of the previously observed moderate blood flow reduction in the right temporal lobe (D).
ASL: arterial spin labeling; ICA: internal carotid artery; MRA: magnetic resonance angiography
Six months after onset, the administration of aspirin was withheld, and the patient returned to the previous job under 5 mg of amlodipine/day without presenting any neurological deficits or symptoms.
Herein, we presented a case of spontaneous bilateral ICAD in a 50-year-old man without any history of atherosclerotic risk factors, solely presenting with sudden onset pulsatile tinnitus. In general, ICAD is a very rare condition, but remains 1 of the major causes of ischemic stroke in younger patients.1,2,7,18) ICAD is responsible only for 2.5% of all strokes, but up to 10%-25% of all ischemic strokes in young and middle-aged patients.1,6,8,18,19)
ICAD can be caused by trauma; various connective tissue disorders, including Marfan syndrome; recent infections; and an elongated styloid process.2,4-6,20,21) The pathomechanisms of spontaneous ICAD, ICAD without this background, remain unknown, but are thought to be multifactorial and involve environmental and intrinsic factors.3,6,22) Conventional risk factors for ischemic stroke, including hypertension, have been reported in patients with spontaneous ICAD. However, the true role of these factors in the mechanism underlying spontaneous ICAD is not clear.23-25) Some authors have suggested that rupture of the vasa vasorum causes intramural hemorrhage, leading to disruption of the intima.2,21) Bilateral carotid artery involvement in ICAD, as seen in our case, is reported in 10%-20% of cases.3,10-13) The causative factors for bilateral spontaneous ICAD are also unknown. Minor neck stress, such as strong coughing, vomiting, and sports activities, may induce injury to the bilateral ICA walls.5) However, in our case, these events did not precede the onset of symptoms.
The classic symptoms of ICAD and their approximate prevalence are as follows: pain in the head, neck, and/or facial regions, 50%; partial Horner syndrome, 50%; lower cranial nerve palsies, 12%; and cerebral and/or retinal ischemic symptoms: 50%-95%.6) ICA dissection causes turbulent flow in the narrow lumen, which can provoke pulsatile tinnitus.6,26,27) In our case, the narrowest part of the true lumen was at the entrance of the carotid canal, which is very close to the right middle ear. Additionally, ASL showed a decrease in blood flow in the right temporal area, suggesting the severity of the narrowing. Considering these facts, it seems reasonable to suspect that extracranial ICA dissection also caused the tinnitus in our case.
The reported prevalence of pulsatile tinnitus in ICAD patients ranges from 5% to 15%.7,14-17) Based on a literature review by Hart et al.4) in 1983, pulsatile tinnitus was the isolated presenting symptom in 4% of cases of ICAD. According to a multi-institutional Cervical Artery Dissection And Ischemic Stroke Patient (CADISP) study, 49 patients (10.2%) present pulsatile tinnitus out of 482 patients with ICAD.17) However, pulsatile tinnitus was an isolated symptom in only 3 patients (0.6%). Thus, isolated pulsatile tinnitus not accompanied by other symptoms, as in our case, is very rare. Nevertheless, physicians should include ICAD in the differential diagnosis of pulsatile tinnitus even when it is unaccompanied by other common symptoms of ICAD. Fortunately, this patient resides near the neurosurgical clinic equipped with an MRI, where the neurosurgeon ordered the MRI study to exclude the possibility of an acoustic tumor and cerebrovascular disorders such as arteriovenous fistula. Fortunately, the initial MRA study included the cervical arteries. Currently, MRA is replacing conventional angiography as the initial diagnostic tool for ICAD.6,8,9) In this case, T1BB images and colored segmentation of the three-dimensional volume rendering MRA clearly differentiated false lumen from true lumen in the initial study. Considering the hyperintensity of the false lumen observed on the T1BB images during the first visit, it is likely that the dissection began several days prior to the onset of tinnitus. This may be supported by reports indicating that T1-intensity typically starts to increase around 3 days after the onset of a carotid artery dissection.28-30)
Because there is currently no randomized trial or high-level evidence to support the use of antiplatelet and antihypertensive drugs in patients with ICAD, especially in those without ischemic stroke, the routine use of these drugs is controversial.6,31,32) However, severe narrowing of the right ICA, accompanied by moderate right cerebral hemispheric flow reduction and aneurysmal dilatation of the right ICA, led us to prescribe these drugs to the patient. The dissection resolved without sequelae within 5 months, which is reported to be the common course of this condition.2,3,6,16)
In conclusion, this report emphasizes the importance of including spontaneous ICAD in the differential diagnosis of the sudden onset of unilateral tinnitus.
The authors wish to thank Haibunsha Kagoshima and Editage for critically reviewing this manuscript and for performing English language editing.
Written consent was obtained from the patient for publication of this case.
None.
Author Ryosuke Hanaya is one of the Editorial Board members of the journal. This author was not involved in the peer-review or decision-making process for this paper.
All authors have no conflict of interest.
