Case Report Perineural trigeminal nerve abscess secondary to Mucor sinusitis: Serial diffusion-weighted MRI and literature review J. Chaganti a , * , D. Marriott b , T. Steel c , J. Donovan a , N. Biggs d a Department of Radiology, St Vincent’s Hospital, Sydney, Australia b Department of Infectious Diseases, St Vincent’s Hospital, Sydney, Australia c Department of Neurosurgery, St Vincent’s Hospital, Sydney, Australia d Department of Otorhinolaryngology, St Vincent’s Hospital, Sydney, Australia Introduction Perineural extension of rhinocerebralzygomycosisis rare.The role of diffusion-weighted imaging (DWI) in per- ineural extension and abscess formation within the nerve has not yet been reported in the literature. This is the first case report highlighting the role of DWI in the perineural extension of zygomycosis.We discuss the differential diagnosis and review the literature. Case report A 45-year-old diabetic male presented with a 3 week history of left-sided facial pain, facial numbness, and high fever despite protracted oral antibiotics.On initial exami- nation left periorbital cellulitis associated with proptosis of the left eye was noted. Fibre optic examination of the nasal cavity revealed necrotic mucosa involving the middle turbinate and the lateral wall of the nose. Computed tomography (CT) demonstrated left maxillary and ethmoid sinus opacification with hyperdensities. Endoscopic debridement of the necrotic material was performed and histopathology ofthe nasalmucosa was consistentwith invasive zygomycosis. Culture of the tissue grew Rhizopus species,a member of the Zygomycetes. Magnetic resonance imaging (MRI)demonstrated an enlarged fifth cranial nerve from the entry root zone to the ganglion (Fig 1). Uniform diffusion restriction with low apparent diffusion coefficient (ADC) values was apparent along the length of fifth nerve as far as the ganglion (Fig 2). Contrast-enhanced studies did not demonstrate perineural or endoneuralenhancement.Enhancing soft tissue was noted in the left pterygopalatine fossa with a lack of enhancementin the ipsilateral cavernous sinus (Fig 1a). There was diffuse enlargement and oedema of V2 and V3 segments of fifth cranial nerve. Similar changes also noted in Vidian nerve on the left side. A diagnosis of rhinocerebral zygomycosis with cavernous sinus thrombosis and possible trigeminal nerve involvement was made. The patient was commenced on liposomal amphotericin B and posaconazole therapy. Despite aggressive surgical treatment vision was lost in the left eye within 24 h. Further debridement with left maxillary orbital exenteration and partial palatal excision was undertaken. Follow-up MRI on day 7 of illness demonstrated continued diffusion restriction with low ADC values in the trigeminal nerve and no contrast enhancement(Fig 3). However, by the third week this had progressed into a well- formed abscess with facilitated diffusion in the core (increased ADC), somewhat restrictive in the periphery and typical ring contrast enhancement(Fig 4). Extension of enhancementinto the left medial temporal lobes was noted. Basalmeningitis was never identified during the course of the illness. Despite the treatment the patient continued to deteriorate and underwent a left temporal craniectomy and drainage of the perineural and temporal lobe abscess. Histopathology of the abscess fluid revealed non-septate hyphae and culture subsequently grew the same Rhizopus species. The patient made a slow recovery and was discharged after 3 months. * Guarantor and correspondent: J. Chaganti,Departments ofRadiology, St Vincent’s Hospital, 390 Victoria Street, Darlinghurst 2010, Sydney, Australia.Tel.: þ61 2 83821111; fax: þ61 2 83823799. E-mail addresses: jchaganti@stvincents.com.au, Rao.joga@gmail.com (J. Chaganti). Contents lists available at ScienceDirect Clinical Radiology j o u r n a l homepage: w w w . e l s e v i e r h e a l t h . c o m / j o u r n a l s / c r a d 0009-9260/$ e see front matter Ó 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2011.05.016 Clinical Radiology 66 (2011) 1106e1109