Congenital cholesteatoma

Hunor Sükösd, MD; Éva Juhász, RT
Medical Imaging Centre, Semmelweis University, Budapest, Hungary

2023-11-13

$A cVRT image shows an oblique fracture line in the scaphoid without dislocation or distraction.$

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History

A 7-year-old girl suffering from bilateral progressive conductive hearing loss, worse on the left side, was presented to the hospital. Physical examination was unremarkable on both eardrums. There were no signs of a middle ear infection present. A CT examination was indicated for further assessment of the middle ear structures. An ultrahigh resolution (UHR) scan mode (Quantum HD) was performed on a dual source photon-counting CT (NAEOTOM Alpha®).

Diagnosis

UHR CT images showed a soft tissue mass in the left middle ear, extending into the mastoid antrum. Erosion of the long process of the incus and the stapes were seen. The eardrum and the scutum were intact and the Prussak’s space was free. No effusion or developmental anomalies were present. CT findings were consistent with congenital cholesteatoma, Potsic stage IV. There were no pathological findings visualized on the right side. An MRI examination was performed to confirm the diagnosis which showed increased diffusion restriction of the mass, characterizing a cholesteatoma. No abnormalities were visualized on the right side in the MRI. As the symptoms were worse on the left side, and there were no pathological findings on the right side, the patient was primarily treated for the left side. Surgical findings confirmed CT diagnosis. A diagnostic tympanoplasty was considered on the other side later on, if the symptoms persisted post-operatively.

Axial images and coronal MPR images show a soft tissue mass in the left middle ear, eroding the long process of the incus and the stapes. The Prussak’s space is free and the scutum was intact. No remarkable findings on the right side. cVRT images show a 3D view of bilateral ossicles – normal on the right and eroded on the left. Note that the input images for cVRT creation are the UHR images reconstructed at 0.2 mm with a very sharp kernel of Hr84. — Courtesy of Medical Imaging Centre, Semmelweis University, Budapest, Hungary

Fig. 1: Axial images (Figs. 1a & 1b) and coronal MPR images (Figs. 1c & 1d) show a soft tissue mass in the left middle ear, eroding the long process of the incus and the stapes. The Prussak’s space (Fig. 1d, arrow) is free and the scutum was intact. No remarkable findings on the right side. cVRT images (Figs. 1e & 1f) show a 3D view of bilateral ossicles – normal on the right and eroded on the left. Note that the input images for cVRT creation are the UHR images reconstructed at 0.2 mm with a very sharp kernel of Hr84.

Comments

Congenital cholesteatomas are inclusion cysts of the ectoderm and are comprised of keratin debris and cholesterol. They are one of the more common causes of pediatric conductive hearing loss besides otitis media with effusion. [1] If undiagnosed, cholesteatomas can lead to the vast destruction of the middle ear structures and permanent damage to the hearing apparatus. Early diagnosis is essential to prevent extensive surgery and preserve hearing. [2] However, most children are asymptomatic and frequently resist attempts to conduct a thorough examination. A pre-operative CT scan is essential in defining the extent of existing pathology, assessing the bony labyrinth and hearing ossicles, as well as planning potential surgery. This especially requires high spatial resolution for evaluating the detailed structures and low dose for pediatric patients.

This case is performed on a dual source photon-counting CT (NAEOTOM Alpha) using an UHR mode, acquiring scan data at 120 x 0.2 mm collimation and reconstructing images at 0.2 mm slice width with a very sharp bone kernel (Hr84). In this mode, each sub-pixel of the photon-counting detector is read-out individually to improve spatial resolution at full dose-efficiency. [3] By using an optimized 70 kV protocol, a very low dose-length product (DLP) of only 92.3 mGy*cm could be achieved, substantially lower than the typical DLPs of 200-400 mGy*cm for this type of examination. Photon-counting CT enables UHR scanning at low radiation dose without substantial increase in image noise, since UHR scan data are acquired at full dose efficiency without additional combs or grids to reduce the detector aperture. Image noise is further reduced by using a refined model based iterative reconstruction approach (Quantum Iterative Reconstruction, QIR). The UHR images can even be used as input for creating a photo-realistic three-dimensional demonstration of the anatomical details, using cinematic volume rendering technique (cVRT), assisting the otologist in setting up an appropriate surgical plan for the patient.

Examination Protocol

Scanner	NAEOTOM Alpha
Scan area	Temporal Bone
Scan mode	UHR mode
Scan length	53.8 mm
Scan direction	Caudo-cranial
Scan time	1.3 s
Tube voltage	70 kV
Effective mAs	340 mAs
Dose modulation	CARE Dose4D
CTDI_vol	13 mGy (16 cm phantom)
DLP	92.3 mGy*cm
Rotation time	0.5 s
Pitch	0.85
Slice collimation	120 x 0.2 mm
Slice width	0.2 mm
Reconstruction increment	0.2 mm
Reconstruction kernel	Hr84, QIR 3

[1] David Walker; Michael J. Shinners. Congenital Cholesteatoma. Pediatr Ann. 2016;45(5):e167-e170.

[2] M.A. El-Bitar et al. Congenital middle ear cholesteatoma: need for early recognition – role of computed tomography scan. International Journal of Pediatric Otorhinolaryngology (2003) 67, 231-235.

[3] Thomas Flohr, et al. Photon-counting CT review. Physica Medica 79 (2020) 126–136.

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