Direct Diagnosis in Radiology
E-Book, Englisch, 272 Seiten, ePub
ISBN: 978-3-13-257967-5
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark
Dx-Direct gets to the point:
- Definitions, Epidemiology, Etiology, and Imaging Signs - Typical Presentation, Treatment Options, Course and Prognosis - Differential Diagnosis, Tips and Pitfalls, and Key References
.all combined with high-quality diagnostic images.
Whether you are a resident or a trainee, preparing for board examinations or just looking for a superbly organized reference: Dx-Direct is the high-yield choice for you!
The series covers the full spectrum of radiology subspecialties including: Brain, Gastrointestinal, Cardiac, Breast, Genitourinal, Spinal, Head and Neck, Musculoskeletal, Pediatric, Thoracic, Vascular
Zielgruppe
Ärzte
Fachgebiete
Weitere Infos & Material
1 Skull Base
2 Petrous Bone
3 Orbit
4 Paranasal Sinuses
5 Pharynx
6 Larynx
7 Oral Cavity
8 Salivary Glands
9 Soft Tissues of the Neck
10 Lymph Nodes
2 Petrous Bone Pneumatization of the Petrous Apex Definition Epidemiology Present in approximately one-third of the population Asymmetrical pneumatization occur in 5 % Fluid retention or aeration disturbance is found in 1 %. Etiology, pathophysiology, pathogenesis Pneumatized petrous apex Congenital anatomical variant. Imaging Signs Modality of choice CT, MRI. CT findings Asymmetrical pneumatization of the petrous apex (resembles the mastoid) Aeration disturbance, fluid retention, or fatty infiltration will opacify the cells and result in a normal appearance with an intact trabecular structure. MRI findings Low signal intensity on T1- and T2-weighted images High T2-weighted signal intensity in cases of fluid retention Increasing T1-weighted signal intensity indicates increasing protein content DD: asymmetrical fatty infiltration. Pathognomonic findings Honeycomb structure of pneumatized petrous apex Fatty infiltration causes high T1- and T2-weighted signal intensities on MRI with no associated mass. Clinical Aspects Typical presentation No clinical complaints Incidental finding. Treatment options Treatment is unnecessary. Course and prognosis Good. What does the clinician want to know? Mass or anatomical variant. Differential Diagnosis Cholesterol granuloma – Mass with high T1- and T2-weighted signal intensity – No enhancement after gadolinium administration Epidermoid, mucocele – Elliptical mass – Low T1-weighted signal intensity – No enhancement after gadolinium administration Tumors – Mass with low T1-weighted signal intensity – Moderate enhancement after gadolinium administration Fig. 2.1 Bilateral pneumatization of the petrous apex. CT appearance resembles the aerated trabecular structure of the normal mastoid. Fig. 2.2a–c Asymmetrical fatty infiltration of the petrous apex. Detected incidentally on MRI based on the high signal intensity in the T1-weighted (a) and T2-weighted (b) images. CT (c) shows normal bony structure with fat-equivalent attenuation values and no mass lesion. Tips and Pitfalls Presumptive diagnosis of cholesterol granuloma or tumor in the absence of mass effect Accurate differentiation may require CT scans (intact trabecular structure!) in addition to MRI and/or follow-up. Selected References Greess H et al. CT und MRT des Felsenbeins. HNO 2002; 50(10): 906–919 Moore KR et al. ‘Leave me alone’ lesions of the petrous apex. AJNR Am J Neuroradiol 1998; 19(4): 733–738 Yetiser S et al. Abnormal petrous apex aeration. Review of 12 cases. Acta Otorhinolaryngol Belg 2002; 56: 65–71 Otosclerosis, Otospongiosis Definition Epidemiology Present in approximately 1% of the population Autosomal dominant mode of inheritance Female predominance (approximately two thirds) Bilateral occurrence in 80–85% of cases. Etiology, pathophysiology, pathogenesis Osteodystrophy of the labyrinth Etiology uncertain Replacement of endochondral bone persisting in the petrous bone by cancellous (spongy) bone, which progressively calcifies to form plaques (“spongiosis”) Fenestral otosclerosis is more common (approximately 85%) than the cochlear or retrofenestral form (approximately 15%) The cochlear form almost always coexists with fenestral sclerosis. Imaging Signs Modality of choice CT (high-resolution). CT findings Circumscribed, usually punctate elliptical lucency in the petrous bone, starting at the anterior rim of the oval window Cochlear, circumscribed, curved, or semicircular hypodense area in the bone Later, progressive ossification of the oval window. MRI findings May show slightly increased signal intensity on T2-weighted images Active disease (with bone transformation) may show punctate foci of enhancement after gadolinium administration. Pathognomonic findings Circumscribed hypodensity of the petrous bone at the anterior rim of the oval window or around the cochlea. Clinical Aspects Typical presentation Conductive hearing loss (fenestral type) Sensorineural hearing loss (cochlear type) Fenestral and cochlear types may coexist Tinnitus. Treatment options Stapedioplasty. Course and prognosis Usually the progression of hearing loss cannot be halted or reversed. What does the clinician want to know? Diagnosis DD: other possible causes of hearing loss or tinnitus. Fig. 2.3 Otosclerosis with ill-defined spongy area near the cochlea, with increased sclerosis of the oval window. Differential Diagnosis Fibrous dysplasia – Homogeneous “ground-glass” density increased throughout the petrous bone – Increased density may spare the inner ear Paget disease – Diffuse involvement of the skull base in patients with mono- or polyostotic disease – Combination of bone destruction and repair (foci of increased and decreased density) Postinflammatory new bone formation – Not confined to the oval window Otosyphilis – Diffuse, permeative osteolytic foci Tips and Pitfalls Subtle lesions anterior to the oval window may be missed. Selected References Grampp S et al. CT und MRT erworbener Veränderungen des Innenohrs und Kleinhirnbrückenwinkels. Radiologe 2003; 43(3): 213–218 Weissman JL et al. Imaging of tinnitus: a review. Radiology 2000; 216(2): 342–349 Petrous Bone Anomalies Definition Epidemiology Meatal atresia: 1:3300–1:10000 births Usually an isolated anomaly. Etiology, pathophysiology, pathogenesis Congenital malformations of the external auditory canal or inner ear Genetically determined Triggered by infection or drug toxicity (e.g., thalidomide) Disruption of normal inner ear development (invagination of the otic pit to form the otocyst in the petrous bone; the otocyst later undergoes medial and ventral elongation and evagination to form the semicircular ducts and cochlea). Imaging Signs Modality of choice CT (high-resolution). CT findings Meatal atresia: Area of soft-tissue or bone attenuation occluding the external auditory canal, with normal appearance of the inner ear. Inner ear malformation: Cochlear aplasia Mondini malformation (incomplete cochlear development with a decreased number of turns, possible associated semicircular canal anomaly) Goldenhar syndrome (posterior superior semicircular canal only, expanded lymphatic duct) Vestibular aqueduct syndrome (enlarged endolymphatic sac) Michel dysplasia (complete failure of inner ear development, rare). MRI findings High-resolution steady-state sequences (e.g., CISS) Fluid-filled inner ear structures show an anomalous configuration (e.g., cystic cochlea, absent semicircular canals) Important: Define the internal auditory canal and its structures (vestibulocochlear nerve). Important structures to evaluate: Superior, posterior, and lateral (horizontal) semicircular canals Cochlea (2.5 turns) Normal position and shape of the ossicular chain Normal external auditory canal. Pathognomonic findings Occlusion of the external auditory canal by soft tissue or bone Mondini malformation: Cystic cochlea with missing turns Goldenhar syndrome: Only one semicircular canal. Clinical Aspects Typical presentation Sensorineural hearing loss Secondary delay of speech development Microtia. Treatment options Cochlear implant. What does the clinician want to know? Diagnosis Meatal atresia: Normal inner ear development (ossicular chain, cochlea)? Normal development of neural structures? Fig. 2.4 CT scan of the right petrous bone in a 6-year-old child shows severe inner ear dysplasia and a cystic cochlea. Tips and Pitfalls High-resolution thin-slice CT scanning should not be omitted. Selected References Bamiou DE et al. Temporal bone computed tomography findings in bilateral sensorineural hearing loss. Arch Dis Child 2000; 82(3): 257–260 Benton C et al. Imaging of congenital anomalies of the temporal bone. Neuroimaging Clin N Am 2000; 10(1): 35–53 Graham JM et al. Congenital malformations of the ear and...
