The Utility of Diffusion-Weighted Imaging for Cholesteatoma Evaluation

Abstract

SUMMARY: DWI is a useful technique for the evaluation of cholesteatomas. It can be used to detect them when the physical examination is difficult and CT findings are equivocal, and it is especially useful in the evaluation of recurrent cholesteatoma. Initial DWI techniques only detected larger cholesteatomas, Ͼ5 mm, due to limitations of section thickness and prominent skull base artifacts. Newer techniques allow detection of smaller lesions and may be sufficient to replace second-look surgery in patients with prior cholesteatoma resection.ABBREVIATIONS: ASSET ϭ array spatial sensitivity encoding technique; DWI ϭ diffusion-weighted imaging; EPI ϭ echo-planar imaging; HASTE ϭ half-Fourier acquired single-shot turbo spin-echo; PROPELLER ϭ periodically rotated overlapping parallel lines with enhanced reconstruction; SNR ϭ signal intensity-to-noise ratio; SS TSE ϭ single-shot TSE; TSE ϭ turbo spin-echo C holesteatomas are enlarging collections of keratin within a sac of squamous epithelium and may be congenital or acquired.1 Acquired cholesteatomas generally occur in the middle ear and mastoid, whereas congenital cholesteatomas or epidermoids can occur in other locations, including the cerebellopontine angle, suprasellar cistern, calvarium, and multiple sites in the temporal bone. Congenital cholesteatomas compose only 2% of middle ear cholesteatomas. 2There are multiple theories regarding cholesteatoma development, but most authors believe there is a disruption of the normal process in which skin lining the tympanic membrane migrates externally within the external auditory canal. Retraction pockets, which are invaginations of the tympanic membrane into the middle ear cavity, develop and interfere with this process. These pockets are largely due to chronic otitis media and eustachian tube dysfunction, which can cause negative middle ear pressure. Retraction pockets occur most commonly in the pars flaccida of the membrane and less commonly in the pars tensa. Epithelial ingrowth may occur as a result of this process, and squamous debris can become trapped within these retraction pockets in the middle ear space.1,3 Many authors also believe that there is a hereditary predisposition to the development of acquired cholesteatomas. 2Complications of cholesteatomas are related to bony erosion. Erosion is generally thought to be related to mechanical pressure, though some believe that adjacent granulation tissue, an osteoclast stimulator, or collagenase production is necessary.1,2 Bony erosion can result in destruction of the ossicles, creating conductive hearing loss, labyrinthine fistulas with sensorineural hearing loss and vertigo, facial nerve canal erosion and facial paralysis, and rare intracranial complications, such as meningitis and abscess. 1,2The treatment for middle ear cholesteatomas is surgical excision. Small cholesteatomas limited to the Prussak space without significant bone erosion can often be effectively resected by using a transcanal atticotomy approach with subsequent tympanoplasty. Patients may undergo...

MRI Sequences in Head & Neck Radiology – State of the Art

“…Furthermore, thinner slices can be obtained than with EPI sequences. The SS version of TSE-DWI is a diffusion-weighted HASTE sequence with excellent motion insensitivity and less sensitivity to susceptibility artifacts and geometric distortion than the EPI sequence [41,42]. A non-EPI DWI sequence with periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER or BLADE) has been reported as useful in avoiding geometric distortion.…”

“…The k-space data are acquired in the form of rotating sections (blades). The resulting oversampling of the central k-space leads to an improved signal-to-noise ratio (SNR) and to the reduction of motion and susceptibility artifacts [41,43,44]. RESOLVE DWI is a new approach for obtaining DWI images with high quality, delivering sharp images at high spatial resolution and reduced slice thickness.…”

“Dazed and diffused”: making sense of diffusion abnormalities in neurologic pathologies

“…Cholesteatomas are most commonly acquired rather than being congenital and, when acquired, typically arise from the pars flaccida of the tympanic membrane with extension into Prussak's space [34]. Symptoms result from erosion of adjacent structures, including the middle ear ossicles, inner ear and facial nerve [35]. Treatment is generally surgical, although residual or recurrent disease is more frequent, so second-look surgeries within 6-18 months of initial surgery are commonly performed [35].…”

“…Symptoms result from erosion of adjacent structures, including the middle ear ossicles, inner ear and facial nerve [35]. Treatment is generally surgical, although residual or recurrent disease is more frequent, so second-look surgeries within 6-18 months of initial surgery are commonly performed [35].…”

Non echo planar, diffusion-weighted magnetic resonance imaging (periodically rotated overlapping parallel lines with enhanced reconstruction sequence) compared with echo planar imaging for the detection of middle-ear cholesteatoma

“…The review paper from Schwartz et al 8 (Rochester, Minnesota, USA) assessed several papers (excluding ours). We would strongly argue that their conclusion, that '[t]he [diffusion-weighted imaging] technique may be used in place of second-look surgery…', should be interpreted with caution.…”