Occipital intraosseous dermoid cyst with restricted diffusion on magnetic resonance imaging in a child

Abstract

A 4-year-old girl presented repeatedly with a complicated occipital mass, which was erroneously treated as a pyogenic granuloma. Imaging performed before a planned surgical resection detected an underlying intraoccipital dermoid with a sinus tract to the skin surface and extension into the posterior fossa. This case highlights the value of high-resolution computed tomography imaging for depiction of anatomic details and the value of magnetic resonance imaging for differential diagnosis and surgical management. A comprehensive literature review of intraosseous dermoid cyst and detailed discussion of the differential diagnoses are provided.

Keywords: CT; Dermoid cyst; Intraosseous; MRI; Occipital.

Fig. 1

A 4-year-old girl with intraoccipital dermoid with associated dermal sinus tract. Preoperative MRI. Findings: The calvarial lesion demonstrates content that is of high T2 and low T1 signal (A and B, long arrows), and the lesion has a thick low T2 signal enhancing rim (A and B, short arrows). These imaging findings can be seen in abscess and dermoid cysts. Technique: (A) MRI, 1.5 T, T2, axial plane, TR 2500, TE 85, slice thickness 3 mm. (B) MRI, 1.5 T, T1 + contrast, sagittal plane, TR 615, TE 12, slice thickness 4.5 mm. Contrast: 5 mL MultiHance (Bracco Diagnostics Inc., Cranbury, NJ, U.S.). MRI, magnetic resonance imaging; TE, echo time; TR, repetition time.

Fig. 2

A 4-year-old girl with intraoccipital dermoid with associated dermal sinus tract. Preoperative MRI. Findings: The calvarial lesion demonstrates restricted diffusion with high signal on DWI (A) and low signal on ADC map (B). This finding can be seen both in an abscess and a dermoid cyst. Technique: (A) MRI, 1.5 T, DWI, axial plane, eB1000, TR 6011, TE 82, slice thickness 4 mm. (B) MRI, 1.5 T, DWI, ADC map, axial plane, TR 6011, TE 82, slice thickness 4 mm. ADC, apparent diffusion coefficient; DWI, diffusion weighted imaging; MRI, magnetic resonance imaging; TE, echo time; TR, repetition time.

Fig. 3

A 4-year-old girl with intraoccipital dermoid with associated dermal sinus tract. Preoperative MRI. Findings: Reformatted noncontrast axial 3D T1 images. The lesion is localized within the occipital diploic space (A), with an intracranial extradural component (B, short arrow), and a sinus track traversing through the occipital bone to the overlying skin (B and C, long arrows). Technique: (A-C) Sequential images. MRI, 1.5 T, noncontrast MPRAGE 3D T1, axial plane, TR 14, TE 7, slice thickness 2 mm. MPRAGE, Magnetization-prepared rapid gradient-echo; MRI, magnetic resonance imaging; TE, echo time; TR, repetition time.

Fig. 4

A 4-year-old girl with intraoccipital dermoid with associated dermal sinus tract. Preoperative CT angiogram. Findings: The lesion is located posterior to the torcular (A, short arrow). The sinus tract is noted as a round track with sclerotic borders (A and B, long arrows). Technique: (A) Contrast-enhanced CT angiogram, axial plane, 120 kVP, 240 mA, slice thickness 0.625 mm, contrast: 40-mL Isovue 370, 20-s delay. (B) Contrast-enhanced CT angiogram, sequential image, axial plane, 120 kVP, 240 mA, slice thickness 0.625 mm, contrast: 40 mL Isovue (Bracco Diagnostics Inc. 259 Prospect Plains Road, Building H Monroe Township, New Jersey 08831 USA) 370, 20-s delay. CT, computed tomography.

Fig. 5

A 4-year-old girl, s/p excision of the intraoccipital dermoid with associated dermal sinus tract. Postoperative course was complicated by abscesses presenting with acute symptoms of slurred speech and ataxia required postoperative MRI. Findings: The patient's postoperative course was complicated by right cerebellar abscesses. Postcontrast T1W demonstrates several adjacent rim-enhancing lesions (A, arrows) with corresponding hyperintense signal on DWI (B) and hypointensive signal on ADC restricted diffusion (C). Surgical cavity is marked with an asterisk (A-C). Technique: (A) MRI, 1.5 T, postcontrast T1W, TR 9383, TE 5, slice thickness 2 mm. Contrast: 3.5 mL MultiHance. (B) MRI, 1.5 T, DWI, axial plane, eB1000, TR 6412, TE 82, slice thickness 4 mm. (C) MRI, 1.5 T, ADC, axial plane, TR 6412, TE 82, slice thickness 4 mm. ADC, apparent diffusion coefficient; DWI, diffusion weighted imaging; MRI, magnetic resonance imaging; TE, echo time; TR, repetition time.