Challenge Cases Case 151 History: adult with skeletal deformity. Legend: B) The line to assess for basilar invagination courses from the hard palate to the undersurface of the occiput or to the posterior margin of the foramen magnum (B). The dens should be less than 5 mm above this line. Note the segmentation anomalies, kyphoscoliosis, and foramen magnum stenosis. Differential diagnosis of causes of platybasia and basilar invagination: Paget’s disease, rheumatoid arthritis, osteogenesis imperfecta, osteomalacia, Klippel- Feil syndrome. Case 152 History: young adult with hearing loss after treatment for same. Legend: Axial high resolution CT scan of the temporal bone shows a focus of demineralization (long arrow). The stapes prosthesis (short arrow) does not have its piston set in the vestibule and was not transmitting sound well. Differential diagnosis: otosyphilis, osteogenesis imperfecta, otospongiosis. Case 153 History: child with trismus, pain. Legend: Axial CT scan reveals a soft tissue mass (arrows) associated with lysis of the left mandible. Differential diagnosis: Ewing’s sarcoma, Langerhans’ cell histiocytosis, neuroblastoma, lymphoma/leukemia, metastasis. Case 154 NO IMAGES AVAILABLE. History: elderly man with solid, painful right-sided neck mass. Differential diagnosis: soft tissue sarcoma, muscular lymphoma, hemangiopericytoma, malignant fibrous histiocytoma. Case 155 History: young adult with facial discomfort, skin rash and mild proptosis. Legend: A) Note the thickening of the greater wing of the sphenoid (arrow) with minimal soft tissue causing left lateral rectus muscle displacement. The bone shows periosteal reaction extending to the lateral orbital wall. Differential diagnosis: osteomyelitis, Ewing’s sarcoma, osteosarcoma, histiocytosis, SAPHO syndrome. Case 156 History: middle-aged man presenting with nasal obstruction and right divergent strabism. Legends: C) Axial T2WI shows an isointense well defined lesion (arrow) occupying the right anterior ethmoid cells and extending to the medial wall of the right orbit. D) Axial T1WI shows the homogeneous bright signal of this lesion (arrow). Differential diagnosis: soft tissue rhabdomyosarcoma, synovial sarcoma, chondrosarcoma, myositis ossificans. Case 157 History: middle-aged woman with paresthesias and weakness in the right arm. Legends: The bony protuberance (arrow) on the axial (A) and coronal (B) images may represent either a cervical rib from C7 or an enlarged transverse process. Either of these may lead to brachial plexopathy and/or thoracic outlet syndrome. Differential diagnosis: fibrous bands, cervical rib, fracture and callous, apophysomegaly. Case 158 NO IMAGES AVAILABLE. History: japanese young adult with palpable neck mass. Differential diagnosis: Kikuchi’s disease, Kawasaki’s disease, Castleman’s disease, metastatic lymphadenopathy, amyloidosis, Kimura’s disease, Rosai Dorfman disease, lymphoma, papillary carcinoma of the thyroid gland, HIV adenopathy. Case 159 NO IMAGES AVAILABLE. History: post-op child with facial dysmorphism. Differential diagnosis: mandibular hypoplasia, Forrest Gump, Pierre Robin syndrome, Treacher Collins syndrome. Case 160 History: young adult with bilateral weakness in the intrinsic hand muscles. Legends: A, B) Bilateral enlargement and enhancement of the lower cervical nerve roots as they exit the foramina is present (arrows). Differential diagnosis: neurofibromatosis, chronic inflammatory demyelinating neuropathy (CIPD), multiple schwannomas, Guillain-Barré syndrome, mononeuritis multiplex, Dejerine-Sottas Disease, Charcot-Marie-Tooth disease. Case 161 NO IMAGES AVAILABLE. History: elderly man with palpable painful neck mass. Differential diagnosis: malignant fibrous histiocytoma, nodular fasciitis, fibrosarcoma, lymphoma. Case 162 History: teenager with limitation of movement in the neck, torticollis. Legends: A- D) Whether the head is in neutral (A), head turned to the right (B), head turned to the left (C) or coronal neutral position (D), the distance from the dens to the left C1 anterolateral arch (arrow) is widened compared to the right side. This indicates fixed rotatory subluxation. Differential diagnosis: traumatic etiology, Grisel inflammatory etiology, normal variation. Case 163 History: middle-aged obese woman with headaches, visual blurring. Legends: A, B) T2-weighted scans show reversed cupping of the optic nerve head insertion on the posterior globes, deforming the smooth contour of the rounded sphere. Differential diagnosis: papillitis, pseudopapilledema, patulous optic nerve sheath complexes, papilledema, optic nerve head drusen. Case 164 NO IMAGES AVAILABLE. History: young adult with bilateral cervical adenopathy, parotid enlargement. Differential diagnosis: lymphoma, sarcoidosis, mastocytosis, amyloidosis, mononucleosis, sinus histiocytosis with massive lymphadenopathy (Rosai- Dorfman). Case 165 History: middle-aged woman with difficulty breathing, stridor. Legend: A) Moderate thickening of the walls of the trachea is evident on this axial post- contrast CT scan. Differential diagnosis: infections (TB, papillomatosis, croup, histoplasmosis), neoplasms (lymphoma, squamous cell carcinoma, minor salivary gland lesions), metabolic/ acquired (amyloidosis, asthma, tracheopathia osteochondroplastica), radiation, post-operative granulation, Wegener’s granulomatosis, sarcoidosis. Case 166 History: young adult with sound-induced vertigo. Legends: Oblique coronal (A) and sagittal (B) images show absence of the bone (arrow) overlying the superior semicircular canal. Differential diagnosis of causes of bone dehiscence: post-operative change, meningocele, trauma, congenital/idiopathic, cholesteatoma, chronic otitis media. Case 167 History: voice change in a young man. Legends: B) Axial T2-weighted scan shows a bright lesion in the supraglottic region with a focal low intensity area within it (arrow). C) This lesion avidly enhances on post gad axial T1 scan and the signal of the focal area within the lesion remains dark (arrow). Differential diagnosis: venous vascular malformation with phleboliths, chondroid lesion, amyloidoma and post-traumatic dystrophic calcification. Case 168 History: teenager with conductive hearing loss and a blue mass seen on otoscopy. Legends: A, B) Axial CT scans through the temporal bone show a non-erosive mass (arrow) infiltrating the right middle ear cavity. This was said to be blue in color on otoscopy. Parts of the ossicles are engulfed by the mass. C) The coronal CT scan confirms that the mass (arrow) seems to conform to existing constraints of the epi and hemotympanum rather than aggressively eroding bone. Differential diagnosis: cholesteatoma, epidermoid, glial choristoma, schwannoma, hemangioma. Case169 History: young adult with right-sided hearing loss. Past history of meningitis. Legends: A-D) Axial high resolution CT scans through the temporal bone show foci of increased density/ossification (black arrows) within the “lumen” of the right cochlea. Differential diagnosis: meningitis, perilymphatic fistula, labyrinthitis ossificans, post- traumatic hemolabyrinth. Case 170 History: young adult after renal transplant with tonsillar pain. Legend: A) A right parapharyngeal non-enhancing mass (arrows) is seen posteromedial to the medial pterygoid muscle. The mass causes deformity of the right palatine tonsil. Differential diagnosis: pleomorphic adenoma, schwannoma, lymphoma, sarcoma, abscess, posttransplant lymphoproliferative disorder. Case 171 History: elderly woman with left facial pain, twitching. Legends: A) The axial raw data image shows a vessel (arrow) in close proximity to the root entry zone of the left trigeminal nerve. By virtue of the size and course this appeared to be a vein. B) The coronal scan post contrast confirms the apposition of the vessel (arrow) to the fifth cranial nerve. Differential diagnosis: vascular compression may be by the superior cerebellar artery > anterior inferior cerebellar artery > both arteries > veins > basilar artery. Case 172 NO IMAGES AVAILABLE. History: teenager with neck pain. Differential diagnosis: lymphoma, rhabdomyosarcoma, metastasis, plasmacytoma, Langerhans’ cell histiocytosis. Case 173 History: history of resection for papillary carcinoma of the thyroid gland with I-131 adjuvant therapy. Legends: A) Note the minimally enhancing soft tissue anterior to the carotid sheath on the right side (long arrow) and in the tracheoesophageal groove (short arrow). Disease in the latter location may affect the recurrent laryngeal nerve. The relative absence of enhancement may reflect the absence of “functioning” tissue since degree of enhancement of the thyroid gland and its function often correlate. B) The mass extends inferiorly to encase the inominate artery on the right (arrow). Differential diagnosis: radiation fibrosis, granulation tissue, reactive thymus, recurrent papillary carcinoma of the thyroid gland. Case 174 NO IMAGES AVAILABLE. History: young adult with toothache. Differential diagnosis: periapical cyst, dentigerous cyst, adenomatoid odontogenic tumor, ameloblastoma, myxoma. Case 175 NO IMAGES AVAILABLE. History: young adult with facial fullness and pain. Differential diagnosis: lymphoma, olfactory neuroblastoma, small cell neuroendocrine tumor, inverted papilloma, aggressive fungal sinusitis, squamous cell carcinoma, adenocarcinoma, sinusitis complication. Case 176 History: middle-aged woman with acute sensorineural right-sided hearing loss. Legends: A) Postcontrast T1-weighted scan suggests an enhancing mass in the right cochlea