Possible diagnosis
Case 103
【Progress】He got explanation about MRI findings and possible diagnosis. Although he had nothing symptomatic, our neurologist advised him to receive health screening using MRI every year.
【Discussion】
Multiple system atrophy (MSA) is supposed to be caused by abnormal accumulation of protein called alpha-synuclein in both neuron and oligodendroglia (in case of Parkinson disease and Lewy body dementia, synuclein deposit in neuron only)(1 - 3). The initial symptom often occurs urine disorder (incontinence) and progressively impairs other neurological disorders. MSA is classified into two types: MSA-cerebellum (MSA-C) and MSA-Parkinson (MSA-P). MSA-C was previously called olivopontocerebellar atrophy. The symptoms of MSA-C are predominant of cerebellar symptoms such as ataxia (muscle discoordination), dysarthria, dys-chewing, dysphagia and dyspnea. Meanwhile, MSA-P was previously called striato-nigral degeneration. The symptoms of MSA-P are predominant of Parkinson signs and symptoms such as rigid muscle, slow movement, tremor and difficulty bending arms and legs. MSA-C occurs more than MSA-P in Japan (1 - 3).
The characteristic findings of MSA on axial images of MRI with T2WI are cruciform linear high signal intensity in the pons (hot cross bun sign) and hyperintense rim in the putamen (hyperintense putamen rim sign) (4 – 10). There is also atrophy of pons, middle cerebellar peduncle and cerebellum. The site of cruciform line corresponded to the selective loss of transverse and longitudinal ponto-cellebellar neurons and the pontine raphe which contain serotonin. The atrophy of raphe neurons indicates the malfunction of serotonin (one of the chemo-transmitters) pathway. MSA progresses over 1-18 years (1 – 3). In our case, MRI with T2WI showed hot cross bun sign and hyperintense putamen rim sign (Fig. 1). These signs are not always to be the determinant sign for MSA. Our patient did not suffer any neural disorders but possible MSA in the future.
BPAS (basi-parallel anatomical scanning) is obtained by the method of positive and negative reversal of CSF (cerebrospinal fluid)-hydrography scanned by heavy-T2WI. It can visualize outer surface of basilar artery and vertebral artery. Meanwhile, MRA (magnetic resonance angiography) is obtained by the method of three dimensional MIP (maximum intensity projection) originally from time of flight scanning. It can visualize blood flow in the vessel, suitable to see the vessel lumen. Then, combining with these two images, are possible to differentiate hypoplasia or aplasia from dissecting aneurysm or occlusion of the vertebral artery and the basilar artery (11 – 13). Vertebral artery is categorized into four segments; V1, from the branching to entering the transverse foramen of C6; V2, through the transverse foramen from C6 to C2; V3, from exit of the transverse foramen of C2, winding tortuously and posteriorly around C1 to entering the dura at the foramen magnum: V4, from the foramen magnum to the basilar artery formed by the fusion of the contralateral vertebral artery (8). Then, BPAS covers only V4 segments of bilateral vertebral arteries. In our case, BPAS showed the existence of V4 segment of the left vertebral artery, while MRA showed the tapering occlusion of the left vertebral artery (Fig. 2). Further, MRI with T2WI showed no flow void of the left vertebral artery (Fig. 3), indicating occlusion of the left vertebral artery.
【Summary】
We present a seventy one-year-old male who appeared in our hospital to receive medical check for his brain. MRI showed crossing line-formed hyperintense at pons (hot cross bun sign) and slit-like hyperintense at putamen (hyperintense putamen rim sign), indicating possible multiple systemic atrophy (MSA). Further, BPAS, T2WI and MRA showed occlusion of the left vertebral artery. We should keep in mind that although hot cross bun sign and hyperintense putamen rim sign are characteristic findings of MSA, they are not always determinant. Further, the contrast of BPAS, MRA and T2WI is crucial to differentiate the occlusive diseases from hypoplasia or aplasia of the vertebral artery and the basilar artery.
【References】
1.Multiple-system atrophy.Fanciulli A et al. N Engl J Med. (2015)
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6.Ozawa T, et al. The spectrum of pathological involvement of the striatonigral and olivopontocerebellar systems in multiple system atrophy: clinicopathological correlations. Brain. 2004;127 (Pt): 2657-71. doi:10.1093/brain/awh303 - Pubmed citation
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10.Khan S, et al. Imaging of vertebral artery stenosis: a systematic review. J Neurol Neurosurg Psychiatry. 2007 Nov; 78(11): 1218–1225.
11.Morimoto K, et al. Incidence of unilateral distal vertebral artery aplasia: evaluation by combining basiparallel anatomic scanning-magnetic resonance imaging (BPAS-MRI) and magnetic resonance angiography. Jpn J Radiol. 2009 Apr;27(3):151-5. doi: 10.1007/s11604-008-0313-0. Epub 2009 May 3.
12.Katsuno M et al. Diagnosis of vertebral artery dissection with basiparallel anatomical scanning magnetic resonance imaging. J Nippon Med Sch. 2011;78(6):367-73.
13.Itabashi R, et al. A dilated surface appearance on basiparallel anatomic scanning-magnetic resonance imaging is a useful tool for the diagnosis of spontaneous vertebral artery dissection in lateral medullary infarction. J Stroke Cerebrovasc Dis. 2014 May-Jun;23(5):805-10. doi: 10.1016/j.jstrokecerebrovasdis.2013.07.003. Epub 2013 Aug 15.
2018.5.9