Radiologic Evaluation of Petrous Apex Masses. Pavan Kavali, MS-IV Morehouse School of Medicine November 16, 2009

Transcription

1 Radiologic Evaluation of Petrous Apex Masses Pavan Kavali, MS-IV Morehouse School of Medicine November 16, 2009

2 Roadmap Petrous Apex Anatomy Patient D.S.: Clinical Presentation Differential diagnosis of masses in the petrous apex of temporal bone Patient Course Acknowledgements References

3 Petrous Apex Anatomy Petrous portion of the temporal bone is pyramidal and is wedged in at the base of the skull between the sphenoid and occipital Consists of a base, apex, anterior, inferior and posterior surfaces. Apex: angular interval between the posterior border of the great wing of the sphenoid and the basilar part of the occipital

4 Axial CT Anatomy

5 Our Patient AI: Clinical History D.S. is a 44 year old man with a four day history of left facial droop Noted difficulty in whistling and drinking from a cup Seen at the Winchester ER where a CT scan was performed which revealed a 3-4 cm posterior fossa mass that extends into the bone and the cerebellum He denies any headache, visual changes, loss of coordination, or other sensory or motor deficits. Past Medical History Meniere s Disease with total deafness of left ear Hypertension Depression/Anxiety

6 Our Patient AI: Initial Imaging Findings Axial CT, patient AI Image Source: BIDMC (PACS) Heterogeneous erosive mass centered within the posterior left temporal bone, eroding into the middle ear cavity, jugular foramen and carotid canal.

7 Our Patient AI: CT and CT-A Findings Axial CT showing heterogeneous mass extending into the posterior left temporal bone CT-Angiogram confirming the findings of the reference head CT from Winchester ER.

8 Our Patient AI: Differential Diagnosis Primary Considerations Endolymphatic Sac Tumor Cholesterol Granuloma of Petrous Apex Lipoma Chondrosarcoma Paraganglioma Acoustic Schwannoma Internal Carotid Artery Aneurysm Cholesteatoma of Petrous Apex

9 Endolymphatic Sac Tumors (ELST) The endolymphatic sac is located at the end of endolymphatic duct lies within dura of the posterior fossa Slow growing tumor that arises from cells lining endolymphatic sac Most sporadic Mutations and allelic deletions of von Hippel-Lindau (VHL) tumor suppressor gene plays a role If bilateral, VHL disease is present Histologically benign Clinical Presentation Most Common Signs/Symptoms Sensorineural hearing loss 100% Facial Nerve Palsy 60% Pulsatile Tinnitus 50% Vertigo 20% Average Age at Surgical Resection 36 years

10 Endolymphatic Sac Tumor MR Imaging Findings Peripheral rim of increased signal intensity is strongly indicative of early endolymphatic sac tumor Hyperintense foci within tumor matrix on T1 (80%) Along tumor margin when tumor < 3 cm Within tumor matrix when tumor > 3 cm Flow voids (focal low signal areas on T1) when tumors > 2 cm T2 Weighted Images Common to see inhomogeneous signal Bone fragments show low signal T1 with Contrast Heterogeneous enhancement CT Imaging Findings Intramural bone spicules moth-eaten appearance noted

11 Companion Patient 1: CT Findings CT through the petrous ridge demonstrates bone erosion at the site of the endolymphatic sac tumor, typical of the locally aggressive behavior of this tumor

12 Companion Patient 1: MR Images T1 MRI demonstrates high signal intensity Post-contrast T1 image demonstrates intense enhancement within the tumor focus

13 Cholesterol Granuloma of Petrous Apex (CGPA) Most common lesion of the petrous apex. Reaction to a foreign body (typically to cholesterol deposits) Due to occlusion of the mastoid air cells and degradation of accumulated hemosiderin to cholesterol Leads to an inflammatory reaction and progressive granuloma formation Clinical Presentation Hearing loss most common Vestibular dysfunction Headache, tinnitus, facial spasms and diplopia also seen

14 CGPA Imaging Findings MRI T1: High Internal Signal Hemorrhage, break-down products, cholesterol crystals T2: High Internal Signal Peripheral dark hemosiderin ring FLAIR: High Internal Signal without attenuation T1 + Contrast: No internal enhancement CT Well-defined, smoothly expansile mass Lesions show focal bony dehiscence Can also evaluate adjacent carotid canal and otic capsule MR more sensitive than CT to evaluate recurrence

15 Companion Patient 2: CT Images Axial CT demonstrates a smoothly expansile mass lesion through the left temporal bone Coronal CT scan confirms the findings of a smoothly expansile mass in the left temporal bone. Courtesy of Dr. Rafael Rojas

16 Companion Patient 2: MR T1 and T2 Weighted Images Courtesy of Dr. Rafael Rojas Bright signal observed on T1 and T2 weighted images in the tumor matrix.

17 Lipoma of CPA-IAC Congenital fatty lesion that is benign Current hypothesis for development of lipomas: Maldevelopment of meningeal precursor tissue Maldifferentiation of mesoderm into lipocytes as opposed to arachnoidal cells Hyperplasia of fat cells within the pia Clinical Presentation Young adult that typically presents with progressive unilateral sensorineural hearing loss With compression of CN VIII, tinnitus (40%) and vertigo (45%) is also seen in patients With compression of CN VII, facial nerve weakness/spasms are also seen Trigeminal neuralgia is seen in about 15% of patients with nerve root entry zone compression

18 Lipoma Imaging Findings MRI T1: High signal mass in the cerebellopontine angle T2: Intermediate fat-intensity lesion FLAIR: High signal mass continues to be seen T1 + Contrast: No enhancement seen if fatsaturated T1 + C sequences are seen. CT Non-enhancing, well-circumscribed lesion seen Use Hounsfield units to determine nature of the mass

19 Companion Patient 3: MR Images CT shows a hypointense lesion in the CPA Courtesy of Dr. Rafael Rojas MRI T1WI: Seen again is an avidly enhancing, wellcircumscribed lesion at the CPA

20 Chondrosarcoma of Petrous Apex Malignant tumor of cartilaginous origin Tumor matrix is entirely chondroid Severity is based on histological grading Typically occurs near the petrous apex if it occurs in the skull base Clinical presentation similar to other petrous apex lesions CT scan used to evaluate extent of bony destruction MR scan typically shows enhancement on T1- and T2-weighted images.

21 Companion Patient 4: CT Images Axial CT showing a chondrosarcoma showing an isodense mass and bony dehisence at the petrous apex of the left temporal bone. Coronal CT showing a large mass that is isodense Courtesy of Dr. Rojas

22 Companion Patient 4: MR Images T1W1 image shows a peripherally enhancing mass at the petrous apex as well as encroaching the cerebellopontine angle. T2W1 image shows a heterogeneously enhancing mass Courtesy of Dr. Rojas

23 Back to Our Patient Patient was sent from Winchester ER to BIDMC for definitive care He continued to exhibit the same symptoms while at BIDMC as well Further characterization of the mass was needed using an MRI with and without contrast.

24 Our Patient AI: Axial MRI Findings MR T1 Axial Image Heterogeneous 4.5 x 2.0 x 3.4 cm mass centered within and growing out of the left temporal bone Striking T1 hyperintensity seen Image Source: BIDMC (PACS)

25 Our Patient AI: MR Findings MR T2 Axial Image Continued to be seen is a heterogeneous, T2 hyperintense mass along the petrous apex Mass extends into and expands the internal auditory canal on the left. The cochlea and semicircular canals are poorly defined on the left side. Image Source: BIDMC (PACS)

26 Our Patient AI: MR Findings MR Axial FLAIR Image The FLAIR image exhibits avidly enhancing mass in the petrous apex also causing mass effect on the left cerebellum. Image Source: BIDMC (PACS)

27 Our Patient AI: Sagittal MR Sagittal MR T1WI showing a hyperintense, heterogeneous mass Image Source: BIDMC (PACS)

28 Our Patient AI: Initial BIDMC Final Report Impression: Heterogeneous mass centered within the left temporal bone with osseous erosion and mild mass effect. It is difficult to appreciate any significant enhancement given the intrinsic T1 hyperintensity, with probable intra-lesional hemorrhage. There is a broad differential including an endolymphatic sac tumor or cholesterol granuloma. Less likely considerations would include metastatic disease, a primary osseous lesion or an unusual aggessive nerve sheath tumor.

29 Our Patient AI: Hospital Course As mentioned earlier, patient s history of prior severe anxiety attacks contributed to his initial discharge from the hospital without any further neurosurgical workup. Since the patient was in stable condition and surgery was non-emergent, patient was counseled extensively to come back for a definitive procedure to remove the mass. Patient came back a week later and underwent resection of the mass.

30 Our Patient AI: Final Diagnosis Final Path Report Papillary neoplasm consistent with endolymphatic sac tumor

31 Our Patient AI: Post-Surgical Result MR Axial T1 Image Partial resection of the previously identified hyperintense and partially enhancing lesion in the left temporal bone Resection of the mass seen more medially but the left hyperintense area persists Image Source: BIDMC (PACS)

32 Acknowledgements Dr. Rafael Rojas, BIDMC Radiology Dr. Brian Livingston, BIDMC Radiology Dr. Gillian Lieberman, BIDMC Radiology Maria Levantakis, BIDMC Radiology

33 References Kim HC et al. Petrous apex cholesterol granuloma presenting as endolymphatic hydrops: a case report. Clin Exp Otorhinolaryngol. 2(3): Epub 2009 Mendenhall, et al. Management of Acoustic Neuroma American Journal of Otolaryngology. 2004; 25: Cohen JE et al. Endolymphatic sac tumor: staged endovascular-neurosurgical approach. Neurol Res. 25(3): , 2003 Richards PS, Clifton AG. Endolymphatic sac tumors. J Laryngol Otol. 117(8):666-9, 2003 Choyke PL et al. Von Hippel Lindau Disease: Genetic, Clinical and Imaging Features. Radiology 146: , tml