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Clinical radiology quiz
Quixxes Am J Otolaryngol 1254-55,
1991
Clinical Radiology Quiz ROY A. HOLLIDAY, MD, AND PETER M. SOM, MD
A 40-year-old man with a history of otitis media in childhood complained of hearing loss and fullness in the right ear following a recent infection. Routine otoscopic examination was limited by
crusting of the superior and posterior portions of the tympanic membrane. Based on the following images, what is the most likely diagnosis?
54
55
HOLLIDAYANDSOM
DISCUSSION The clinical history and physical findings are highly suggestive of acquired middle ear cholesteatoma. Coronal image A is surprisingly normal. The malleus is intact and no mass is present between the malleus and the scutum. The anterior tympanic cavity (protympanum) is clear. The scuturn is not eroded. Coronal image B (obtained 3 mm posterior to A) demonstrates several abnormalities. Only the body of the incus is identified. The long and lentitular processes are absent, replaced by a soft tissue mass that abuts the cochlear promontory and fills the oval window. The attic, however, is clear. Axial image C confirms the destruction of the long process of the incus, also demonstrating the extension of the mass into the recesses of the posterior tympanic cavity, including the round window niche and sinus tympani. The central mastoid tract is clear. The computed tomography (CT) diagnosis of acquired cholesteatoma is indicated by the presence of a nondependant soft tissue mass in the tympanic cavity. Definitive diagnosis requires CT evidence of bone destruction, either of the ossicular chain or the walls of the tympanic cavity. The location of the soft tissue mass, the pattern of ossicular destruction, and the degree of ossicular displacement will vary with the type of acquired cholesteatoma evaluated. The majority of acquired cholesteatomas involve the pars flaccida and Prussak’s space. Virtually all of the boundaries of Prussak’s space can be identified on CT. The lateral border consists of the pars flaccida and the inferolateral wall of the epitympanum (attic), while the medial border consists of the head of the malleus and the body of the incus. The inferior border is defined by the short process of the incus. Only the lateral mallear ligament, which forms the superior and anterior borders of Prussak’s space, cannot be readily identified on CT. In the case presented here, only a tiny portion of Prussak’s space is occupied by the cholesteatoma. Pars flaccida cholesteatomas characteristically displace the heads of the malleus and incus me-
dially, and preferentially erode the head of the malleus as well as the body and long process of the incus. While the long process of the incus is eroded in this case, the malleus and body of the incus are intact. In this case, the scutum was intact. Erosion of the scutum, the classic sign of a pars flaccida cholesteatoma on polytomography, has proven to be an unrealiable sign on CT. Pars flaccida cholesteatomas have been documented on CT in the absence of scutum erosion, while erosions of the scutum can be demonstrated without soft tissue masses in the tympanic cavity. This case demonstrates all of the typical features of a pars tensa cholesteatoma. Pars tensa cholesteatomas are also known as “sinus” cholesteatomas because of their tendency to spread to the sinus tympani and other recesses of the posterior tympanum. Spread from the posterior tympanum is typically superiomedial or superiolatera1 toward the additus. The majority of the epitympanum is usually spared unless the mass is very large. Pars tensa cholesteatomas tend to erode the long process of the incus first. This patient underwent a tympanomastoidectomy shortly following this CT scan. On microscopic examination, a perforation of the posterior pars tensa was identified. A cholesteatoma was removed from the middle ear opposite the oval window. The long process of the incus, as well as the stapes, was eroded. Computed tomography is unable accurately to assess the integrity of the stapes in the presence of a cholesteatoma. Despite this limitation, it remains a valuable asset in the evaluation of patients with suspected cholesteatoma, particularly those in whom otoscopic evaluation is limited. SUGGESTED READING Holliday, RA: Inflammatory diseases of the temporal bone: Evaluation with CT and MR. Semin Ultra CT MR 1989; 10213-235 Swartz JD: Cholesteatoma of the middle ear: Diagnosis, etiology and complications. Radio1 Clin North Am 1984; 22:15-35
1991
Clinical Radiology Quiz ROY A. HOLLIDAY, MD, AND PETER M. SOM, MD
A 40-year-old man with a history of otitis media in childhood complained of hearing loss and fullness in the right ear following a recent infection. Routine otoscopic examination was limited by
crusting of the superior and posterior portions of the tympanic membrane. Based on the following images, what is the most likely diagnosis?
54
55
HOLLIDAYANDSOM
DISCUSSION The clinical history and physical findings are highly suggestive of acquired middle ear cholesteatoma. Coronal image A is surprisingly normal. The malleus is intact and no mass is present between the malleus and the scutum. The anterior tympanic cavity (protympanum) is clear. The scuturn is not eroded. Coronal image B (obtained 3 mm posterior to A) demonstrates several abnormalities. Only the body of the incus is identified. The long and lentitular processes are absent, replaced by a soft tissue mass that abuts the cochlear promontory and fills the oval window. The attic, however, is clear. Axial image C confirms the destruction of the long process of the incus, also demonstrating the extension of the mass into the recesses of the posterior tympanic cavity, including the round window niche and sinus tympani. The central mastoid tract is clear. The computed tomography (CT) diagnosis of acquired cholesteatoma is indicated by the presence of a nondependant soft tissue mass in the tympanic cavity. Definitive diagnosis requires CT evidence of bone destruction, either of the ossicular chain or the walls of the tympanic cavity. The location of the soft tissue mass, the pattern of ossicular destruction, and the degree of ossicular displacement will vary with the type of acquired cholesteatoma evaluated. The majority of acquired cholesteatomas involve the pars flaccida and Prussak’s space. Virtually all of the boundaries of Prussak’s space can be identified on CT. The lateral border consists of the pars flaccida and the inferolateral wall of the epitympanum (attic), while the medial border consists of the head of the malleus and the body of the incus. The inferior border is defined by the short process of the incus. Only the lateral mallear ligament, which forms the superior and anterior borders of Prussak’s space, cannot be readily identified on CT. In the case presented here, only a tiny portion of Prussak’s space is occupied by the cholesteatoma. Pars flaccida cholesteatomas characteristically displace the heads of the malleus and incus me-
dially, and preferentially erode the head of the malleus as well as the body and long process of the incus. While the long process of the incus is eroded in this case, the malleus and body of the incus are intact. In this case, the scutum was intact. Erosion of the scutum, the classic sign of a pars flaccida cholesteatoma on polytomography, has proven to be an unrealiable sign on CT. Pars flaccida cholesteatomas have been documented on CT in the absence of scutum erosion, while erosions of the scutum can be demonstrated without soft tissue masses in the tympanic cavity. This case demonstrates all of the typical features of a pars tensa cholesteatoma. Pars tensa cholesteatomas are also known as “sinus” cholesteatomas because of their tendency to spread to the sinus tympani and other recesses of the posterior tympanum. Spread from the posterior tympanum is typically superiomedial or superiolatera1 toward the additus. The majority of the epitympanum is usually spared unless the mass is very large. Pars tensa cholesteatomas tend to erode the long process of the incus first. This patient underwent a tympanomastoidectomy shortly following this CT scan. On microscopic examination, a perforation of the posterior pars tensa was identified. A cholesteatoma was removed from the middle ear opposite the oval window. The long process of the incus, as well as the stapes, was eroded. Computed tomography is unable accurately to assess the integrity of the stapes in the presence of a cholesteatoma. Despite this limitation, it remains a valuable asset in the evaluation of patients with suspected cholesteatoma, particularly those in whom otoscopic evaluation is limited. SUGGESTED READING Holliday, RA: Inflammatory diseases of the temporal bone: Evaluation with CT and MR. Semin Ultra CT MR 1989; 10213-235 Swartz JD: Cholesteatoma of the middle ear: Diagnosis, etiology and complications. Radio1 Clin North Am 1984; 22:15-35