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Kazuhisa Yoshifuji, Nobuhito Morota, Yoshinori Omori, Izumi Koyanagi, and Nobuhiro Mikuni

OBJECTIVE

Spinal lipomas are congenital malformations. They do not express tumorous growth but are found to increase in volume like other normal subcutaneous fat tissue during the early postnatal period. To understand the natural course of volume changes in spinal lipomas, the authors measured the changes in size of spinal lipomas together with the normal subcutaneous fat in relation to BMI.

METHODS

A total of 27 patients with conus spinal lipoma excluding lipomyelomeningocele who underwent MRI twice before surgery (on initial diagnosis and immediately preoperatively) were included. Patients’ ages at the time of the first MRI ranged from 0 to 32 months (mean 2.9 months, median 1 month). Candidates were categorized by age into three groups: < 1 month, 1–2 months, and ≥ 3 months. The growth rate of the spinal lipomas (in three directions), change in thickness of the normal subcutaneous fat, growth rate of the normal spinal canal (dorsoventral direction), and change in BMI were retrospectively analyzed between the three groups.

RESULTS

The mean interval between MRI studies was 83.1 days. During this time, the mean lipoma growth rates were 199%, 149%, and 133% in the dorsoventral, lateral, and craniocaudal directions, respectively (with 100% representing the first measurement). The mean change in the thickness of the normal subcutaneous fat was 183%. The mean growth of the normal spinal canal was 111%. The mean increase in BMI was 124%. These rates were all significantly higher in the younger groups. There was no significant difference in the growth rates between the lipoma and the subcutaneous fat in every age group. In contrast, the growth rate of the lipoma significantly exceeded that of the spinal canal in patients younger than 3 months. The subarachnoid space around the lipoma became obstructed in 35.3%, and spinal cord distortion occurred in 48.1% of the patients younger than 3 months.

CONCLUSIONS

Spinal lipomas rapidly increase in volume before the age of 3 months and especially in infants younger than 1 month. Their features closely correlate with the physiological growth of the normal subcutaneous fat and the increase in BMI. The rapid growth of lipomas suggests the importance of close observation in this period, keeping in mind the typical anatomical changes of lipomas and their surrounding structures.

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Hime Suzuki, Takeshi Mikami, Tomoyoshi Kuribara, Kazuhisa Yoshifuji, Katsuya Komatsu, Yukinori Akiyama, Hirofumi Ohnishi, Kiyohiro Houkin, and Nobuhiro Mikuni

OBJECTIVE

Medullary streaks detected on fluid-attenuated inversion recovery (FLAIR) imaging have been considered to be reflected ischemic regions in pediatric moyamoya disease. The purpose of this study was to evaluate these medullary streaks both clinically and radiologically and to discuss associated pathophysiological concerns.

METHODS

The authors retrospectively reviewed data from 14 consecutive pediatric patients with moyamoya disease treated between April 2009 and June 2016. Clinical and radiological features and postoperative imaging changes were analyzed. In 4 patients, hyperintense medullary streaks on FLAIR imaging (HMSF) at the level of the centrum semiovale were detected.

RESULTS

The HMSF were coincident with hyperintense medullary streaks on a T2-weighted image, though they were not completely coincident with the vasculature on either a T2*-weighted image or contrast-enhanced CT. Analysis revealed significantly higher values in terms of MR angiography scores, number of flow voids of the basal ganglia, and the presence of the medullary artery in the group with HMSF than in those without. In contrast, the presence of white matter damage was significantly less frequent in the HMSF group. All HMSF disappeared after surgery, and the mean apparent diffusion coefficient at the same level was significantly reduced postoperatively.

CONCLUSIONS

Although HMSF should be associated with collateral circulation in moyamoya disease, other factors may be involved, including stagnated cerebrospinal fluid or vasogenic edema that is relevant to the impaired state of the white matter. Findings in this study provide insight into the pathophysiological basis of the perivascular space in moyamoya disease.