DOI: https://doi.org/10.21203/rs.2.206/v3
Isolated posterior inferior cerebellar artery dissections (iPICADs) can cause subarachnoid hemorrhages or infarctions1. The incidence of iPICAD had been thought to be very rare. The reports of iPICAD with stroke, however, are increasing with the advancement of high-resolution MRI techniques. Surgical and endovascular treatments for hemorrhagic stroke cases and medical treatments using antiplatelet or anticoagulant agents for ischemic stroke cases have been reported. The treatment strategy for iPICADs with headache only, however, is not yet established because the reports on nonstroke iPICADs are still rare. Herein, a nonstroke iPICAD case that spontaneously healed is reported.
A 48-year-old male, who had no past medical or traumatic history and no family history of cerebral artery dissections, suddenly felt a severe, throbbing headache on the right side and came to the OIKE clinic on the fourth day following onset. MRI examinations showed a tiny dissection-like finding (pearl and string sign-like) on his right proximal segment (tonsillomedullar segment) of posterior inferior cerebellar artery (PICA) (Fig. 1A). No intramural hematoma, double lumen finding or intimal flap were observed, but PICA dissection (PICAD) could not be ruled out, and the patient was therefore carefully observed, with continuous monitoring of blood pressure, heart rate and other vital signs; also, he was hydrated sufficiently and given analgesic anti-inflammatory agents (a nonsteroid anti-inflammatory drug: Loxoprofen Sodium Hydrate 60-300 mg a day). MRA on the seventh day revealed the chronological shape change of the PICA, strongly suggesting PICAD (Fig. 1B). The other MRI sequences showed no infarctions or hemorrhages (Fig. 1C, D). Conventional angiography was not performed because of the patient’s rejection, and his PICA was observed by serial high-resolution MRI examinations. The inner and outer diameters of the dissected PICA were measured by MRI T1-weighted high-resolution vessel wall imaging (HRVWI) (Fig. 1F) and T2-weighted HRVWI (basi-parallel anatomical scanning (BPAS); Fig. 2), respectively. The severity of the headache was assessed by Numerical Rating Scale (NRS) every day. Two weeks after the onset of headache, the diameter of the dissected vessel grew to the maximum size (Fig. 2A), though the patient’s headache improved markedly on the eighth day (Fig. 3). At that time, surgical or endovascular treatment to prevent subarachnoid hemorrhage was recommended; however, the patient, who had been relieved of severe headache, desired to continue conservative therapy. Four weeks after the onset, the dissection finding on MIP images began to improve. Eight weeks after the onset, his PICA looked almost normal on MIP and T1-weighted HRVWI, though the outer diameter was still bulging on a T2-weighted HRVWI (BPAS). Finally, four months after the onset, the outer diameter was observed to be almost normal in size and shape (Fig. 2). The patient has resumed activities, such as marathon racing, again.
MRI examinations showed no apparent intramural hematoma, double lumen, or intimal flap indicating artery dissection. PICA is a tiny vessel and it is possible that these findings could not be detected even by high-resolution MRI techniques. Recently, the chronological changes in the size and shape of the affected vessels have been considered to be one of the criteria for diagnosing cervicocephalic artery dissections, including intracranial small vessels such as PICA. Table 1 shows the Spontaneous Cervicocephalic Arterial Dissections Study (SCADS) criteria. According to the criteria, the patient was diagnosed with PICAD (criteria 5, 7, and 8 matched)2.
Conventional angiography may have provided useful information to confirm the patient’s PICA condition; however, for this patient, serial high-resolution MRI examinations, including HRVWI, were sufficient to confirm the condition of the vessel. T1-weighted HRVWI was used to confirm the intraluminal size change. The outer diameter was followed by basi-parallel anatomical scanning (BPAS), one type of T2-weighted HRVWI3.
Among cervicocephalic artery dissections, vertebral artery dissections (VADs) are common, and the therapeutic strategy for VAD has been established4. The reports of iPICAD with stroke are increasing with the advancement of high-resolution MRI techniques, but those with headache only are still limited. In the last decade, over 70 cases of iPICAD have been found in the literature, but almost all the cases included subarachnoid hemorrhages5 or infarctions6. There have been only two non-stroke iPICAD cases reported, and one of these was diagnosed with coexisting VAD7. As mentioned above, PICAD is often a tiny finding, even with high-resolution MRI techniques, and can therefore be overlooked unless accompanied by a symptomatic stroke. The patient in the present case was fortunately suspected to have iPICAD at the beginning of the clinical course and was followed using high-resolution MRI examinations.
It is interesting that the severity of the patient’s headache might be related to the chronological changes of the MRI findings. The patient felt a severe, throbbing headache continuously while MRI findings of PICAD were worsening. After the occipital pain was relieved, his PICAD finding stopped worsening and gradually improved on MRI examinations.
Conservative therapy is usually selected for nonstroke VAD, whereas the therapeutic strategy for iPICAD with headache only is not yet determined. The other case of the reported two iPICAD with headache only was surgically treated to prevent subarachnoid hemorrhage because the dissection finding by radiological examination was progressive8. It might be permissible to perform any surgical and/or endovascular treatments in such a case. However, as in the present case, it is also possible that iPICAD with headache only may heal spontaneously.
BPAS: basi-parallel anatomical scanning
CTA: computed tomographic angiography
DSA: digital subtraction angiography
DWI: diffusion weighted image
FLAIR: fluid-attenuated inversion recovery
HRVWI : high resolution vessel wall imaging
iPICAD: isolated posterior inferior cerebellar artery dissection
MIP: maximum intensity projection
MRA: magnetic resonance arteriogram
MRI: magnetic resonance imaging
NRS: numerical rating scale
VAD: vertebral artery dissection
Ethics approval and consent to participate
This manuscript was approved by the institutional review board (OIKE Clinic ethics committee, approval reference number 18-01), and informed consent for participation was obtained from the patient.
Consent for publication
Written informed consent was obtained from the patient for publication of this report and any accompanying images.
Availability of data and materials
All data generated or analyzed during this study are included in this published article and its supplementary information files.
Competing interests
None.
Funding
None.
Acknowledgements
None.
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Figure 4. The inner diameters and areas of the dissected PICA were measured using cross-sectional view of T1-weighted HRVWI.
Figure 5. The outer diameters of the dissected PICA were measured using original data of T2-weighted HRVWI (BPAS).