Background The “hot cross bun” (HCB) sign, a cruciform hyperintensity in the pons on magnetic resonance imaging (MRI), has gradually been identified as a typical finding in multiple system atrophy, cerebellar-type (MSA-C). Few reports have evaluated the sensitivity of an HCB, including a cruciform hyperintensity and vertical line in the pons, which precedes a cruciform hyperintensity, in the early stages of MSA-C. Moreover, the difference in frequency and timing of appearance of an HCB between MSA-C and spinocerebellar ataxia type 3 (SCA3) has not been fully investigated.Methods This study investigated the time at which an HCB and orthostatic hypotension (OH) appeared in 41 patients with MSA-C, based on brain MRI and head-up tilt test. The MRI findings were compared with those of 26 patients with SCA3. The pontine signal findings on T2-weighted MRI were graded as 0 (no change), 1 (a vertical T2 high-intensity line), or 2 (a cruciform T2 high-intensity line), with grades 1 or 2 considered as an HCB. OH 30/15 was defined as a decrease in systolic blood pressure of > 30 mmHg or diastolic blood pressure of > 15 mmHg.Results Among the 24 patients with MSA-C within 2 years from the onset of motor symptoms, an HCB was detected in 91.7%, whereas OH 30/15 was present in 60.0%. Among the 36 patients with MSA-C within 3 years from the onset of motor symptoms, a grade 2 HCB was detected in 66.7% of those with MSA-C but in none of those with SCA-3.Conclusions HCB is a highly sensitive finding for MSA-C, even in the early stages of the disease. A grade 2 HCB in the early stage is an extremely specific finding for differentiating MSA-C from SCA-3.
This article reviewed brain mechanism of the lower urinary tract (LUT). Among autonomic nervous systems, LUT is unique in terms of afferent pathophysiology; bladder sensation is perceived soon after the storage phase and throughout the voiding phase. Within the brain, this is measured in experimental animals by the firing of single neurons and in humans by evoked potentials/functional neuroimaging. The evidence indicates that sphincter information goes up to the precentral motor cortex and other brain areas, and bladder information goes up to the insular cortex (IC)/anterior cingulate (ACG) and further to the prefrontal cortex (PFC). Another LUT-specific phenomenon is efferent pathophysiology: detrusor overactivity (exaggerated micturition reflex) occurs in brain diseases such as stroke (focal disease) and dementia with Lewy bodies (diffuse diseases, may overlap with each other). With the turning off and on of the brain-switch of micturition (at the periaqueductal gray [PAG]), there is a bladder-inhibitory PFC-IC/ACG-hypothalamus-PAG pathway, with interconnections via the PFC with a PFC-nigrostriatal D1 dopaminergic pathway and a PFC-cerebellar pathway. Brain diseases that affect these areas may cause a loss of the brain's inhibition of the micturition reflex, leading to detrusor overactivity. This has a significant clinical impact on patients and requires appropriate management.
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