On the left, outer cortical bone is destroyed (arrow) with subperiosteal abscess formation (asterisk). In pediatric patients, a significantly higher prevalence of total opacification occurred in the tympanic cavity (80% versus 19%, P = .002) and mastoid air cells (90% versus 21%, P = .046). Radiology Cases of Acute Mastoiditis Axial CT with contrast of the brain with bone windows (left) shows partial opacification of the left mastoid air cells and a lower image with soft tissue windows (right) shows inflammation in the left neck soft tissues at the level of the left mastoid air cells. The best one can do is to describe the extent of the previous operation, the state of the ossicular chain (if present), and the aeration of the postoperative cavity. In the expected position of the superior canal only a bump is seen. A minor deformity of the cochlear apex is visible there is no separation of the second and third turn and the bony modiolus is absent. On CT the detection of otosclerosis can be difficult to the inexperienced eye because the spread of the disease is often symmetrical. (arrow) Petromastoid canal The final analysis covered 31 patients. The cochlea has no bony modiolus. It is connected to the long process of the incus (yellow arrow). These images are of a 50-year old man who presented with a left- sided retraction pocket and otorrhoea. An incidental finding of fluid in the mastoid air cells in an otherwise healthy individual can be approached like any case of otitis media, whereas fluid in the mastoid combined with destruction of surrounding bone in a seriously ill patient is a medical emergency. If this patient would be a trauma victim, the canal could easily be confused with a fracture line (arrow). Its diameter is around 0.5 mm. Pediatric patients (16 years of age or younger) numbered 10. ELST is a rare entity. Temporal Bone Imaging. These patients tend to present with a variety of symptoms including hemotympanum, tympanic membrane perforation, vertigo, facial nerve paresis, nystagmus, retroauricular ecchymosis, hemorrhagic otorrhea, and hearing loss [ 1 ]. fluid-filled cochlea while CT depicts small calcifications. The lateral semicircular canal is partially filled with dense material, compatible with labyrinthitis ossificans. A conductive hearing loss is the result. The study was supported by the Helsinki University Central Hospital Research Funds. On the left coronal images of the same patient. CT is usually the initial technique of choice for imaging patients with AM. the 8th nerve, which precludes cochlear implantation. The posterior wall of the external auditory canal and the ossicular chain are intact. Antibiotics may or may not be appropriate, and factors such as history of recurrent infections, presence of resistant organisms in the community, and patient age should be considered. It can be confused with a fracture line. On the left images of a 54-year old male several years after head trauma, followed by left-sided hearing loss. In larger cohorts, these may still prove valuable markers of severe disease. Statistical analysis was conducted by a biostatistician with NCSS 8 software (NCSS, Kaysville, Utah). Prostheses made of Teflon can be almost invisible. Intratemporal and extracranial complications predominated over intracranial complications (Table 2). images of the left external carotid artery before embolisation and the common At the superior and anterior part of the mastoid process the air cells are large and irregular and contain air, but toward the inferior part they diminish in size, while those at the apex of the process are frequently quite small and contain marrow. tympanic cavity and mastoid air cells with soft tissue. On the left images of a metallic stapes prosthesis. Right ear for comparison (blue arrow). Key clinical signs include a bulging tympanic membrane, protruding pinna, abundant discharge from and pain in the ear, a high fever, and mastoid tenderness.9 Patients presenting with advanced disease and late complications may also present with sepsis, meningeal symptoms, or facial nerve paralysis. In patients with an intact tympanic membrane, opacification of the tympanic cavity may have a different prognostic impact. This article was externally peer reviewed. intensity along mastoid air cells representing a thin film of fluid overlying the mucosa; and 3, T2 hyper-intensity opacifying the mastoid air cells represent- Am J Roentgenol 171:14911495, Little SC, Kesser BW (2006) Radiographic classification of temporal bone fractures: clinical predictability using a new system. The image on the left shows a dislocated tube lying in the external auditory canal. MR imaging is mainly reserved for detection or detailed evaluation of intracranial complications or both. Lowered SI in the ADC was detectable in 16 of 26 patients (62%). The posterior canal is normal. On the left a patient with a bilateral large vestibular aqueduct. On the left images of a 56-year old male, who is a candidate for cochlear implantation. The posterior wall of the external auditory canal and the ossicular chain are intact. The petromastoid canal or subarcuate canal connects the mastoid antrum with the cranial cavity and houses the subarcuate artery and vein. Learn more about Institutional subscriptions, Lantos JE, Leeman K, Weidman EK, Dean KE, Peng T, Pearlman AN (2019) Imaging of temporal bone trauma: a clinicocradiologic perspective. Address correspondence to . We do not capture any email address. Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. Osteomas are less common and mostly unilateral and pedunculated. MRI can also demonstrate absence of Exostoses are caused by contact with cold water and mostly seen in swimmers and surfers. Compared with CSF, they also showed intramastoid signal changes in T1 spin-echo, T2 TSE, CISS, and DWI sequences; and intramastoid, outer periosteal, and perimastoid dural enhancement. B) Bilateral mastoiditis in patient with acute otitis media complicated by temporary facial nerve paralysis. The average duration of symptoms before MR imaging was 12.9 days (range, 090 days). A large cholesteatoma has resulted in a so called 'automastoidectomy', with severe erosion of the lateral tympanic cavity wall and destruction of the ossicular chain. The aim of this presentation is to demonstrate imaging findings of common diseases of the temporal bone. The cochlea is normal. Note: No air present in No fracture line could be seen across the inner ear. The vestibule is relatively large (arrow). When to Go to Peniche. In some patients, marked signal changes and intense intramastoid enhancement were detected early in AM, even on the second symptomatic day, and therefore cannot be related to chronic conditions only.8. High jugular bulb or jugular bulb diverticulum, Auditory ossicles, especially the long process and lenticular processes of the incus as well as the head of the stapes, In advanced cholesteatoma the presence of aerated parts of the middle ear denote a mass and not an effusion, Non-dependent soft tissue particularly favors a mass. A small amount of soft tissue (arrow) is visible between the scutum and the ossicular chain but no erosion is present. No erosions are present. On the left a 2-year old boy with bilateral bony external auditory canal atresia. There is fluid in the mastoid cavity with extensive destruction (coalescence) of the bony septa within the mastoid process (white arrow). The extent of ossicular chain malformation can vary from a fusion of the mallear head and incudal body to a small clump of malformed ossicles, which is often fused to the wall of the tympanic cavity. ADVERTISEMENT: Supporters see fewer/no ads. On the left a 16-year old boy, examined preoperatively for a cholesteatoma of the right ear. The image shows a subluxation of the incudomallear joint (arrow). Hyperintense-to-WM SI in DWI was associated with a shorter duration of intravenous antibiotic treatment (mean, 1.9 versus 5.0 days; P = .029). If the bony separation between the jugular bulb and the tympanic cavity is absent, it is termed a dehiscent jugular bulb. Solve this simple math problem and enter the result. Associations between dichotomized MR imaging findings and background or outcome parameters were determined with the Fisher exact test for categoric data and the Mann-Whitney U test for numeric data. A large vestibular aqueduct is seen (black arrow). Indeed, almost all cases of otitis, whether sterile or infectious, will result in uid lling the mastoid air cells.5 The majority of pa- Due to the relatively small number of patients, the original MR imaging scoring groups were dichotomized by summation of the original scoring groups into groups of comparable sizes before statistical analysis. Indeed, almost all cases of otitis, whether sterile or infectious, will result in fluid filling the mastoid air cells.5 The majority of patients with otitis media are, unfortunately, not imaged; because of this we are unaware of the real incidence of mastoiditis in these patients. There is fluid in the mastoid cavity but no evidence of destruction of the bony septa within the mastoid process (black arrow). An entry into the antrum is created, but most of the mastoid air cells are still present. Tumors of the temporal bone are rare. On the left a coronal reconstruction of the same patient. A P value of < .05 was considered statistically significant. Neuroimaging Clin N Am 29(1):129143, Article Stapes prostheses are inserted in patients with otosclerosis to replace the native stapes, which is fixed in the oval window. Intratemporal abscess was defined as a nonanatomic cavity inside the temporal bone with an enhanced wall and marked diffusion restriction inside it. There is a widening and shortening of the lateral semicircular canal. Therefore, a combination of both On the left a 49-year old male with left sided conductive hearing loss. Cholesteatoma is believed to arise in retraction pockets of the eardrum. (3) CT shows erosion of the long process of the incus and of the stapedial superstructure. In addition to detecting intracranial complications, MR imaging could be recommended for pediatric patients due to its lack of ionizing radiation. On the left images of a 68-year old woman who experienced a traumatic head injury 50 years ago. Continue with the images of the left ear. Running through this bony canal is a tube called the endolymphatic duct. The blue arrow indicates the cochlear aqueduct coursing towards the cochlea. On the left angiographic This question is for testing whether or not you are a human visitor and to prevent automated spam submissions. We will discuss them because their CT appearance is very typical. Although opacification degree in the tympanic cavity usually was lower than that in the distal parts of the temporal bone, when 100%, it indicated a decision to perform surgery. There is a dislocation of the incus with luxation of the incudo-mallear and incudo-stapedial joint (blue arrow). There is a transverse fracture through the vestibule and facial nerve canal (arrows). ISBN:160913446X. MR images of bilateral AM with duration of symptoms of 12 days on the left and fewer than 6 days (36 days) on the right side. 1. A large vestibular aqueduct is associated with progressive sensorineural hearing loss. CT shows a rounded mass (arrow) in the attico-antrotomy with erosion of the tegmen tympani. also suffered from chronic otitis media. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. Thank you for your interest in spreading the word on American Board of Family Medicine. In rare cases, untreated mastoiditis can sometimes result in increased pressure within the mastoid cavity, which is relieved by movement of the fluid through the tympanomastoid fissure; this causes postauricular tenderness and inflammation. Findings from this review showed that the mastoid air cells' size with respect to age differs among populations of different origins. On T2 FSE, among 31 patients, the SI was hypointense to CSF in 28 (90%) and iso- or hypointense to WM of the brain in 4 (13%). Cochlear implantation is performed in patients with sensorineural deafness due to degeneration of the organ of Corti.After implantation of a multichannel electrode a wide array of electrical pulses can be produced to stimulate the acoustic nerve.The electrode is inserted into the scala tympani of the cochlea via the round window or via a drill hole directly into the basal turn (cochleostomy).Post-operatively its position can be evaluated with CT. ImagesEight-year-old boy with bilateral cochlear implants. CT demonstrates a soft tissue mass between the ossicular chain and the lateral tympanic wall, which is eroded. A) Acute uncomplicated mastoiditis in an asymptomatic patient. Their accuracy in detecting clinically relevant AM and their true prognostic value remain to be clarified by larger studies. Additionally, SNHL was associated with obliteration of the aditus ad antrum by enhanced tissue (P = .023) and outer cortical bone destruction (P = .015). Instead of the normal two-and-one-half turns, there is only a normal basal turn and a cystic apex. Amy F. Juliano, Daniel T. Ginat, Gul Moonis. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. A longitudinal fracture is visible, which courses anteriorly to the cochlea through the region of the geniculate ganglion (arrows). It contains a chain of movable bones, which connect its lateral to its medial wall, and serve to convey the vibrations communicated to the tympanic membrane across the cavity to the internal ear. In coalescent AM, infection causes osteolysis of the bony septa or cortical bone, which can further lead to intra- and extracranial complications. The malleus handle is present. In acute posttraumatic paralysis a fracture line through the facial nerve canal - usually in the tympanic part - can be observed, sometimes with a bony fragment impinging on the canal. Calcification of superior semicircular canal on the left (yellow arrow). J Am Board Fam Med 26(2):218220, Mafee MF, Singleton EL, Valvassori GE, Espinosa GA, Kumar A, Aimi K (1985) Acute otomastoiditis and its complications: role of CT. Radiology 155:391397, Saat R, Laulajainen-Hongisto AH, Mahmood G, Lempinen LJ, Aarnisalo AA, Markkola AT, Jero JP (2015) MR imaging features of acute mastoiditis and their clinical relevance. This can include hospitalization and intravenous antibiotics with or without myringotomy or retroauricular puncture7 or, in more severe cases, mastoidectomy.8 If available, images will show fluid in the mastoid cavity with destruction of the bony septa within the mastoid process (Figure 2). On the left axial images of a patient with a reconstruction of the ossicular chain with an autologous incus (arrow) between the ear drum and the stapes. Obliteration degree in different temporal bone subregions (n = 31). 9 Patients presenting with advanced disease and late complications may also present with sepsis, meningeal symptoms, or facial nerve paralysis. RealFeel Shade 56. Normal position in the right ear. It can be accidentally lacerated during a mastoidectomy and therefore should be mentioned in the radiological report when present. MRI can demonstrate fibrous obliteration of the MRI is particularly useful for evaluating the extension of a cholesteatoma into the middle and/or posterior fossa, and for demonstrating possible herniation of intracranial contents into the temporal bone - especially after surgery. There is a cystic component on the dorsal aspect which does not enhance. 2023 by the American Society of Neuroradiology | Print ISSN: 0195-6108 Online ISSN: 1936-959X. Its capability to differentiate among causes of opacification is poor. Elderly persons are most commonly affected with a female predominance. Non-vascular anomalies which can also manifest as a retrotympanic mass: In patients with an aberrant internal carotid artery the cervical part of the internal carotid artery is absent. Provided by the Springer Nature SharedIt content-sharing initiative, Over 10 million scientific documents at your fingertips, Not logged in Emerg Radiol 28, 633640 (2021). Image examples of each scoring category according to signal intensities. Mastoid opacification was defined as hyperintensity within the mastoid air cells on T2-weighted imaging and included fluid and mucosal thickening/edema. Most patients had at least a 50% opacification in the tympanic cavity and total opacification of the mastoid antrum and air cells (Fig 2). As a coincidental finding, there is a plump lateral semicircular canal (yellow arrow) and an absence of the superior canal (blue arrow). On the left an example of bilateral cochlear cleft in a one-year old boy with congenital hearing loss. Both diseases often occur in poorly pneumatized mastoids. On the left a 5-year old boy with bilateral progressive hearing loss. cochlear apex. Clin Radiol 68(4):397405, Article It can be divided into coalescent and noncoalescent mastoiditis. 1Department of Radiology, University of Utah Health Sciences Center, 30 North 1900 East, #1A71, Salt Lake City, UT 84132-2140. It is replaced by the ascending pharyngeal artery which connects with the horizontal part of the internal carotid artery. The petromastoid canal is well seen. The climate in Peniche runs cool compared to the inland Alentejo region and the warmer, southern region of the Algarve. A re-operation was performed and a new prosthesis was inserted. The cochlea develops between 3 and 10 weeks of gestation. It can also occur around the cochlea (retrofenestral otosclerosis). Acute mastoiditis (AM) is a complication of otitis media in which infection in the middle ear cleft involves the mucoperiosteum and bony septa of the mastoid air cells. This is a preview of subscription content, access via your institution. In more severe cases lucencies are also present around the cochlea. * *Money paid to the institution. The value of diffusion-weigthed MR imaging in the diagnosis of primary acquired and residual cholesteatoma: a surgical verified study of 100 patients. contrast. For every patient, only 1 ear was evaluated. Nearly two-thirds (59%) had intramastoid signal intensity higher than that in their brain parenchyma on DWI and low signal on ADC, confirming the true diffusion restriction. On MRI there is usually strong enhancement. The sigmoid sinus bulges anteriorly. 3. The body of the incus, which is lateral to the mallear head is also eroded (arrow). The dura was intact. At otoscopy a blue ear drum is seen. The jugular bulb is often asymmetric, with the right jugular bulb usually being larger than the left. MATERIALS AND METHODS: Medical records and MR imaging findings of 31 patients with acute mastoiditis (21 adults, 10 children) were analyzed retrospectively. Reference article, Radiopaedia.org (Accessed on 01 May 2023) https://doi.org/10.53347/rID-28366, see full revision history and disclosures, superior longitudinal muscle of the tongue, inferior longitudinal muscle of the tongue, levator labii superioris alaeque nasalis muscle, superficial layer of the deep cervical fascia, ostiomeatal narrowing due to variant anatomy. No involvement of the inner ear. CAS ISBN:1588904016. Enter multiple addresses on separate lines or separate them with commas. Mastoid air cells. On the left images of a 14-year old boy with bilateral sensorineural hearing loss. The cochlear aqueduct is a narrow canal which runs towards the cochlea in almost the same direction as the inner auditory canal, but situated more caudally. Sometimes the whole otic capsule is surrounded by these 'otospongiotic' foci, forming the so-called fourth ring of Valvassori. On the left images of a woman who had fallen down from the stairs three days earlier. Trends toward predicting operative treatment were also detectable in regard to total opacification of mastoid air cells (P = .056) and thick and intense intramastoid enhancement (P = .066). The mastoid air cells are traversed by the Koerner septum, a thin bony structure formed by the petrosquamous suture that extends posteriorly from the epitympanum, separating the mastoid air cells into medial and lateral compartments. Small calcification in basal turn of cochlea as a result of labyrinthitis ossificans (arrows). (2013) Radiology. In addition, a cranial magnetic resonance imaging scan may be obtained if intracranial complications are suspected.10. Acute mastoiditis causes several intra- and perimastoid changes visible on MR imaging, with >50% opacification of air spaces, non-CSF-like signal intensity of intramastoid contents, and intramastoid and outer periosteal enhancement detectable in most patients. Infection in these cells is called mastoiditis. Thirty-one patients were analyzed (11 male and 20 female); mean age, 33.4 years (range, 381 years). The scutum is blunted (arrow). A temporal bone fracture can manifest itself with acute signs like bleeding from the ear or acute facial paralysis. Radiographics 40(4):11481162, Northwell Health, 300 Community Drive, Manhasset, NY, 11030, USA, Mayo Clinic Jacksonville, 4500 San Pablo Rd S, Jacksonville, FL, 32224, USA, You can also search for this author in Criteria for generalized pachymeningitis (in contrast to perimastoid dural enhancement) were extensive thickening and enhancement of the dura that extended past the borders of the temporal bone. Based on recent reports,12,13 the diagnostic criteria for AM in our institution were the following: either intraoperatively proved purulent discharge or acute infection in the mastoid process, or findings of acute otitis media and at least 2 of these 6 symptoms: protrusion of the pinna, retroauricular redness, retroauricular swelling, retroauricular pain, retroauricular fluctuation, or abscess in the ear canal, with no other medical condition explaining these findings. Careful inspection is required in order to pick out these thin fracture lines. Gray H. Anatomy of the Human Body, 20th edition. There are several normal variants which may simulate disease or should be reported because they can endanger the surgical approach. Alok A. Bhatt. The middle . The mastoid portion of the facial nerve canal can be located more anteriorly than normal and this is important to report to the ENT surgeon in order to avoid iatrogenic injury to the nerve during surgery. On the left images of a 57-year old male with a slowly progressive glomus jugulotympanicum tumor, visible as a mass on the floor of the tympanic cavity (arrow). In a minority of patients the disease is unilateral. Same patient. Fractures of the inner ear are seen in posttraumatic sensorineural hearing loss. On the left a 22-year old man suffering from persistent otitis. Erosion of the facial nerve canal is difficult to distinguish Notice how the cholesteatoma has eroded the scutum (arrow). The imaging technique of choice usually is CT for its sensitivity in detecting opacification and bone destruction. Before the application of antibiotics to treat otitis media, acute mastoiditis was a common clinical entity, occurring in up to 20% of cases of acute otitis media1 and often requiring emergent mastoidectomy.2 Since the use of antibiotics in the management of otitis media, incidence has decreased significantly.3 Although the incidence of acute coalescent mastoiditis has decreased, the incidence of fluid in the mastoid air cells, which can technically be referred to as mastoiditis, has not changed. He had undergone several ear operations in the past. There is also destruction of the cortical bone separating the mastoid cavity from the sigmoid sinus (open white arrow). On the left images of a patient with a synthetic stapes prosthesis. Clinical aspects and imaging findings between pediatric and adult patient groups were compared with the Fisher exact test. The middle ear is an irregular, air-filled space within the temporal bone. When Is Fluid in the Mastoid Cells a Worrisome Finding? Posttraumatic conductive hearing loss can be caused by a hematotympanum or a tear of the tympanic membrane. At CT a destructive process is seen on the dorsal surface of the petrosal part of the temporal bone with punctate calcifications. Google Scholar. All these findings favor the diagnosis of a cholesteatoma, but at surgery, chronic mastoiditis was found and no cholesteatoma was identified. The most common measurements were the area of air cells. Stage 3: Loss of the vascularity of the bony septa leading to bone necrosis. 2023 Springer Nature Switzerland AG. On the left a large destructive process of the dorsal temporal bone. The following tumors can be seen: On the left bilateral bony lesions of the external auditory canal, typical of exostoses. Patients with acute coalescent mastoiditis will also appear obviously sick; there are no silent cases of acute coalescent mastoiditis. Emergency radiologic approach to mastoid air cell fluid. DWI was included in our protocol to detect purulent secretions and possible intratemporal abscesses.1620 On DWI, most patients (93%) showed variable degrees of signal increase in their mastoid effusions (Table 1). 28 Apr 2023 12:08:20 {"url":"/signup-modal-props.json?lang=us"}, Knipe H, Hacking C, Weerakkody Y, et al. In a retrospective review by Glynn et al,4 retroauricular fluctuance reflective of a subperiosteal abscess was the only clinical sign significantly associated with the need for surgical intervention. Objectives/hypothesis: To investigate whether radiologist-produced imaging reports containing the terms mastoiditis or mastoid opacification clinically correlate with physical examination findings of mastoiditis. & Bhatt, A.A. Part of Springer Nature. Those with MR imaging of the temporal bones available (n = 34) were selected for this study. this favors the diagnosis of cholesteatoma. While describing an X-ray in ENT or Otorhinolaryngology, you need to comment on these points: Plain or Contrast Regions: Mastoid, Nose and PNS or Soft-tissue neck On the left axial and coronal images of a 64-year old male. Unable to process the form. Notice the lucency between vestibule and cochlea as a manifestation of otosclerosis (arrow). case 2These images show an implant which is malpositioned. Clinical Anatomy by Regions. The consequences of the intracranial injuries dominate in the early period after the trauma. Otosclerosis is a genetically mediated metabolic bone disease of unknown etiology. Blockage of the aditus ad antrum was defined as filling of the aditus lumen by enhanced tissue. carotid artery after embolization (blue arrow). Subperiosteal abscesses were detectable in 6 (19%) and were correlated with younger age (mean, 6.0 versus 25.0 years; P = .010) and with retroauricular signs of infection (P = .028). Intense enhancement was associated with younger age (mean, 24.6 versus 42.7 years; P = .019). MRI is more useful for diseases of the inner ear. Almost all of the mastoid air cells are removed. Acute mastoiditis: the role of imaging for identifying intracranial complications, Otogenic intracranial inflammations: role of magnetic resonance imaging, Role of imaging in the diagnosis of acute bacterial meningitis and its complications, Computed tomography and magnetic resonance imaging of pathologic conditions of the middle ear, Imaging of complications of acute mastoiditis in children, Incidental diagnosis of mastoiditis on MRI, Acute mastoiditis in children aged 016 years: a national study of 678 cases in Sweden comparing different age groups, National assessment of validity of coding of acute mastoiditis: a standardised reassessment of 1966 records, Otitic hydrocephalus associated with lateral sinus thrombosis and acute mastoiditis in children, Magnetic resonance imaging in acute mastoiditis, Applications of DWI in clinical neurology, Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging, Diffusion-weighted magnetic resonance imaging, Diffusion-weighted MR imaging of intracerebral masses: comparison with conventional MR imaging and histologic findings, The diagnostic value of diffusion-weighted magnetic resonance imaging in soft tissue abscesses, The value of diffusion-weighted MR imaging in the diagnosis of primary acquired and residual cholesteatoma: a surgical verified study of 100 patients, Apparent diffusion coefficient values of middle ear cholesteatoma differ from abscess and cholesteatoma admixed infection, Acute complications of otitis media in adults, A Novel MR Imaging Sequence of 3D-ZOOMit Real Inversion-Recovery Imaging Improves Endolymphatic Hydrops Detection in Patients with Mnire Disease, CT and MR Imaging Appearance of the Pedicled Submandibular Gland Flap: A Potential Imaging Pitfall in the Posttreatment Head and Neck, Imaging the Tight Orbit: Radiologic Manifestations of Orbital Compartment Syndrome, Thanks to our 2022 Distinguished Reviewers, 2015 by American Journal of Neuroradiology.