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Simple Coccygeal Dimple
KEY FACTS
Terminology
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Synonym: Sacral dimple
Imaging
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Low sacral dimple connecting to coccyx by fibrous tract
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Usually resides within intergluteal cleft
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No intradural extension by definition
-
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Variable size; deeper dimples usually evoke more physician and parental concern
Top Differential Diagnoses
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Dorsal dermal sinus
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Pilonidal sinus
Pathology
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Congenital
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Tract usually atretic; may occasionally be patent with fluid in lumen
Clinical Issues
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Often asymptomatic discovery by parents during diaper change or bathing
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Dimple becomes less conspicuous as patient grows
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No specific treatment indicated; reassure parents
-
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Occasionally presents with acute inflammation or purulent discharge
Diagnostic Checklist
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Important to distinguish from dorsal dermal sinus, which requires surgical excision
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Low dimple opening within intergluteal cleft usually but not always coccygeal dimple
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High dimple position, leaking of fluid more likely dorsal dermal sinus
-
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Look for hypointense tract surrounded by bright fat on MR
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Always mark skin dimple ostium with MR visible marker
Sagittal graphic of the lumbosacral spine demonstrates a low sacral dimple (marked by vitamin E capsule
), which is connected to the coccyx tip by a fibrous tract
. There is no intradural extension, and the conus/intradural structures are normal.
), which is connected to the coccyx tip by a fibrous tract . There is no intradural extension, and the conus/intradural structures are normal.
Sagittal T2WI MR demonstrates a deep low sacral dimple with vitamin E marker capsule
placed. The conus terminates at normal L1 level. The dimple and tract
connect directly to the coccyx
with no intradural extension.
placed. The conus terminates at normal L1 level. The dimple and tract connect directly to the coccyx with no intradural extension.
Sagittal T1WI MR reveals a deep sacral dimple marked for imaging with a vitamin E capsule
. The conus terminates at normal L1 level. The dimple shows typical “spot-welded” proximity to the coccyx via a short fibrous tract
.
. The conus terminates at normal L1 level. The dimple shows typical “spot-welded” proximity to the coccyx via a short fibrous tract .
Axial T1WI MR confirms that the sacral dimple, marked with vitamin E capsule
, and tract
connect directly to the coccyx
without intradural extension.
, and tract connect directly to the coccyx without intradural extension.
TERMINOLOGY
Synonyms
-
Sacral dimple
Definitions
-
Low sacral dimple connecting to coccyx by fibrous tract
-
No intradural extension by definition
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