Saremi et alAJR185 December 2005is a rare condition whereby a gliom - PDF document

M Saremi et al.AJR:185, December 2005is a rare condition whereby a glioma arises fromheterotopic cell nests in the leptomeninges.Leptomeningeal dissemination is an un-common complication of gliomas andotherprimary intraaxial malignancies.Thepresence of a single unexplained en-hancing cranial nerve in a patient with cancerraises the possibility of leptomeningealdissemination.Fig.1„48-year-old woman with metastatic melanoma and meningeal carcinomatosis.A…E, Contrast-enhanced axial (A, B, D, and ) and coronal () T1-weighted images show enhancement and involvement of multiple cranial nerves: oculomotor nerves arrows); trigeminal nerves (arrows); complex of seventh and eighth cranial nerves (arrows); complex of ninth,

tenth, and eleventh cranial nerves (long arrows and ); and hypoglossal nerves (short arrows, Saremi et al.AJR:185, December 2005Perineural tumor extension, a form ofmetastatic disease, involves the spread ofprimary mucosal or cutaneous tumors tononcontiguous regions along nerve sheaths.Perineural tumor spread has been shown inperineural or endoneural tissue planes alonga path of least resistance. Retrograde spreadis significantly more common than ante-grade spread. A series by Parker and Harns-berger [5] found perineural spread occursmost commonly with squamous cell carci-noma and adenoid cystic carcinoma, withthe facial nerve and second and third divi-sions of the trigeminal nerve most fre-quently involved (Fig.

2). Other neoplasticand aggressive infectious processes, such asacute lymphoblastic leukemia, non-Hodgkin’s lymphoma, malignant schwan-noma, aspergillosis, mucormycosis, and ac-tinomycosis, also show perineural extension(Fig. 3). MRI findings of perineural involve-ment include smooth thickening and en-hancement of the nerve, concentric expan-sion of the skull base foramina withFig.3(continued)„43-year-old man with acute lymphoblastic leukemia. and C, Contrast-enhanced axial T1-weighted images show antegrade perineural extension along course of left spinal trigeminal tract and nuclei (arrow) into preganglionic segment of left trigeminal nerve (arrowFig.4„7-year-old girl with tuberculous meningitis. and Contrast-en

hanced axial () and coronal () T1-weighted images show abnormal peripheral enhancement of oculomotor nerves (long arrows). In addition, there is leptomeningeal enhancement of anterior surface of brainstem (short arrows Saremi et al.AJR:185, December 2005is seen in 17–70% of patients and occurs inthe setting of diffuse leptomeningeal tubercu-losis. Impairment has been attributed to is-chemia of the nerve or entrapment of thenerve in basal exudates [7] (Fig. 4). is the mostcommon fungus to involve the CNS. Cryp-tococcal meningitis is one of the typicalpathologic manifestations and can result inoptic neuropathy in both immunocompetentand immunocompromised patients (Fig. 5).Optic neuropathy is a rare complication ofcr

yptococcal meningitis and usually occursin non-AIDS patients. Necrosis of the opticnerves and infiltration of the meningesaround the optic tracts, nerves, and chiasmby cryptococcal organisms have beenobserved [8].Rhinocerebral mucormycosis is a poten-tially devastating fungal infection in diabeticand immunocompromised patients. Sinonasaldisease often progresses to the orbit andcavernous sinus and may be complicated byvascular and perineural invasion and localthrombotic infarction [9] (Fig. 6).Cranial neuroschistosomiasis occurs lesscommonly than the spinal variety and mayarise with any of the clinical forms of thisparasitic infection. Eggs within the CNSinduce a cell-mediated periovular granulo-matous reaction tha

t leads to signs andsymptoms of increased intracranial pressureand focal neurologic signs [10]. AlthoughFig.7„17-year-old boy with neuroschistosomiasis. Contrast-enhanced T1-weighted images show range of involvement of CNS in schistosomiasis.Sagittal image shows enhancing masses within chiasmatic…hypothalamic (short arrow) and pineal (long arrow) regions. Coronal image shows thickened and enhancing trigeminal nerves (arrows Axial image reveals enhancing mass (arrow) in right cerebellopontine angle with extension into internal auditory canal. Saremi et al.AJR:185, December 2005of inflammatory demyelinating polyneurop-athies that include Guillain-Barré and vari-ants, such as Miller Fisher syndrome andpolyneuritis cr

anialis.GranulomatosisIntracranial neurosarcoidosis has a predi-lection for the basal leptomeninges, andinvolvement of every cranial nerve has beendescribed. MRI shows a spectrum of CNSabnormalities including diffuse or nodularthickening and abnormal enhancement ofthe leptomeninges in the basal cisterns andhypothalamic regions [12] (Fig. 10).Perineural spread has also been reported insarcoidosis [13]. Clinical involvement andimaging cranial nerve involvement fre-and clinical resolu-ng resolution [14].Idiopathic hypertrophic cranial pachy-meningitis is a rare disease characterizedby inflammation and fibrosis of the duramater. It remains a diagnosis of exclusionbut may be the presenting manifestation ofgranulomatous

diseases such as sarcoido-sis, Wegener’s granulomatosis, or tubercu-losis. MRI shows focal or diffuse thicken-ing and enhancement of the dura thatencase cranial nerves causing recurrentcranial neuropathies. The oculomotor, ab-ducens, and facial nerves are more fre-quently involved [15].Tolosa-Hunt syndrome consists of painfulophthalmoplegia related to a granulomatousinflammatory process in the cavernous si-nus. MRI findings are nonspecific and in-clude enhancement and abnormal soft tissuein the ipsilateral cavernous sinus and orbitalapex [16] (Fig. 11).Postradiation NeuritisRadiation-induced cranial nerve injury isan uncommon, usually delayed, complicationof radiation therapy or radiosurgery. Cranialnerve deficit

s may be permanent or resolvespontaneously. Loss of the nerve–blood bar-rier due to demyelination and ischemia, coag-pheral fibrosis resultsFig.9„57-year-old man with ophthalmoplegic migraine.A…C, Unenhanced axial () and enhanced axial () and coronal () T1-weighted images reveal smooth enlargement and homogeneous enhancement of cisternal segment of left oculomotor nerve (arrows Saremi et al.AJR:185, December 2005trigeminal and facial schwannomas and thenglossopharyngeal, vagus, and spinal accessorynerve schwannomas (Fig.13). Neurofibroma-tosis 2 is characterized by bilateral vestibularschwannomas. Schwannomas of the other cra-nial nerves occur more frequently in neurofi-bromatosis 2. Enhancing hemangiomas, men-ing

iomas, or metastases may mimic theappearance of early schwannomas.References1.Gebarsk SS, Telian SA, Niparko JK. Enhancementalong the normal facial nerve in the facial canal: MRimaging and anatomic correlation. Radiology 1992;183:391–3942.Williams LS, Schmalfuss IM, Sistrom CL, et al. MRimaging of the trigeminal ganglion, nerve, and theperineural vascular plexus: normal appearance andvariants with correlation to cadaver specimens. J Neuroradiol 2003; 24:1317–13233.Grossman SA, Krabak MJ. Leptomeningeal carci-nomatosis. Cancer Treat Rev 1999; 25:103–1194.Collie DA, Brush JP, Lammie GA, et al. Imagingfeatures of leptomeningeal metastases. Clin Radiol1999; 54:765–7715.Parker GD, Harnsberger HR. Clinical–radiologiciss

ues in perineural tumor spread of malignant dis-eases of the extracranial head and neck. Radio-Fig.12„48-year-old woman with postradiation optic neuritis who presented with loss of vision in left eye 8 months after radiation therapy. Patient had previously undergone resection of adenoid cystic carcinoma of right maxillary sinus. Contrast-enhanced axial T1-weighted image shows enhancement of intracranial portion of left optic nerve (long arrow). Note large enhancing tumor (short arrows) with internal hemorrhage in right temporal lobe.Fig.13„48-year-old woman with schwannoma arising from left inferior vestibular nerve.and Contrast-enhanced axial () and coronal () T1-weighted images show small enhancing tumor (arrows