Beltran, E

Biggi, M

Freeman, C

Grundon, R

Holloway, A

Stewart, J

English

RVC Research Online

  RVC OPEN ACCESS REPOSITORY – COPYRIGHT NOTICE  This is the peer reviewed version of the following article: Beltran, E., Grundon, R., Stewart, J., Biggi, M., Holloway, A. and Freeman, C. (2016), IMAGING DIAGNOSIS — UNILATERAL TRIGEMINAL NEURITIS MIMICKING PERIPHERAL NERVE SHEATH TUMOR IN A HORSE. Veterinary Radiology & Ultrasound, 57: E1–E4. doi:10.1111/vru.12272 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. The full details of the published version of the article are as follows:  TITLE: IMAGING DIAGNOSIS — UNILATERAL TRIGEMINAL NEURITIS MIMICKING PERIPHERAL NERVE SHEATH TUMOR IN A HORSE AUTHORS: Beltran, E., Grundon, R., Stewart, J., Biggi, M., Holloway, A. and Freeman, C. JOURNAL TITLE: Veterinary Radiology & Ultrasound PUBLISHER: Wiley PUBLICATION DATE: January 2016 DOI: 10.1111/vru.12272  1   1  2 IMAGING DIAGNOSIS - UNILATERAL TRIGEMINAL NEURITIS MIMICKING 3 PERIPHERAL NERVE SHEATH TUMOR IN A HORSE 4  5 ELSA BELTRAN, RACHAEL GRUNDON, JENNIFER STEWART, MARIANNA 6 BIGGI, ANDREW HOLLOWAY, COURTENAY FREEMAN  7  8 Corresponding author 9 Elsa Beltran, Department of Clinical Science & Services, The Royal Veterinary College, 10 Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA, United Kingdom. e-mail: 11 ebeltran@rvc.ac.uk 12  13 Key Words: trigeminal nerve, MRI, horse, neuritis 14 Running head: Unilateral trigeminal neuritis in a horse 15 Funding sources: This study was not finacially supported by any organisation or grant 16 Previous presentations or abstracts: This case report was presented as clinical research 17 abstract at the 27th annual symposium of the European College of Veterinary Neurology, 18 18th-20th September, 2014, Madrid, Spain. 19  20  2 Abstract 21 A 16-year-old Warmblood gelding presented with a non-healing corneal ulcer and absent 22 corneal sensation in the left eye. A lesion affecting the maxillary and ophthalmic branches 23 of the left trigeminal nerve was suspected. Magnetic resonance (MR) imaging identified 24 marked thickening of the ophthalmic and maxillary branches of the left trigeminal nerve. 25 The nerve was iso- to hypointense on T1-weighted and T2-weighted images with 26 heterogeneous enhancement. A peripheral nerve sheath tumor was suspected, however 27 granulomatous neuritis was histopathologically confirmed. These inflammatory changes 28 can result in severe nerve enlargement and should be considered with MR findings 29 suggestive of peripheral nerve sheath tumor. 30 31  3 Signalment, History and Clinical Findings 32 A 16-year-old Warmblood gelding was presented with a two-week history of a non-healing 33 corneal ulcer in the left eye. On presentation there was a mid depth stromal ulcer of the left 34 eye with a 4-5 mm fringe of perilimbal vascularisation. The ocular defect covered 70% of 35 the cornea with severe corneal edema precluding deeper ocular examination. A focal area 36 of cellular infiltrate was present at 10 o’clock at the margin of the ulcer and also ventrally 37 along the edge of the ulcer. There was minimal ocular discharge and the eye was open and 38 comfortable. The right eye was normal to ocular examination. Touch testing of the left 39 corneal surface revealed no corneal sensation. A neurological examination was requested. 40  41 Neurological examination revealed normal mental status, posture and gait. Postural 42 reactions were normal in all four limbs. Cranial nerve examination revealed decreased 43 sensation at the medial and lateral canthus of the left eye, the cornea of the left eye, over 44 the maxilla on the left, and in the left nostril. Palpebral reflex was decreased in the left eye, 45 but the menace response was present. Direct pupillary light reflex (PLR) could not be 46 assessed in the left eye due to the severity of the corneal ulcer and edema; however, a 47 normal consensual PLR was present on the right eye. The rest of the neurological 48 examination was normal. Pre-referral haematology and serum biochemistry did not reveal 49 any abnormalities. 50  51 Based on the history, ophthalmic and neurologic examination, a lesion affecting the 52 maxillary and ophthalmic branches of the left trigeminal nerve (CN V) was suspected. The 53 main differential diagnoses were neoplasia and inflammatory/infectious diseases. A MR 54  4 imaging study of the head was recommended in order to investigate the underlying cause.  55 A temporary tarsorrhaphy was placed in the left eye and the horse was started on topical 56 ocular serum and chloramphenicol eye drops every 4 hours.  57  58 Imaging, Diagnosis and Outcome 59 Magnetic resonance imaging of the head was performed under general anesthesia using a 60 1.5-T superconducting magnet (GE Signa Echospeed System, General Electric Medical 61 System, Milwaukee, WI). The horse was position on right lateral recumbency and images 62 were obtained in three planes (dorsal, sagittal and transverse). Sequences included T2-63 weighted (T2W) fast spin echo (FSE), T1-weighted (T1W) FSE before and after 64 administration of intravenous contrast medium (20 ml, gadobenate dimeglumine, 65 MultiHance, Bracco Imaging SpA, Milan, Italy). 3D- Spoiled Gradient Echo (SPGR) 66 pulse sequence was also acquired in transverse plane after contrast medium administration. 67 The MR images showed severe enlargement of the ophthalmic and maxillary branches of 68 the left trigeminal nerve from the level of middle cranial fossa, extending rostrally through 69 the orbital fissure and round foramen respectively, measuring about 2 cm in diameter 70 compared to 0.4 cm on the right side. The left infraorbital nerve was markedly thickened 71 along the length of the infraorbital canal. The trigeminal nerve enlargement was visible on 72 all sequences, however the T1W images acquired in transverse and sagittal planes showed 73 better definition of the lesion. The left orbital fissure, round foramen, and infraorbital canal 74 were enlarged by the markedly thickened left trigeminal nerve. The bony margin of these 75 structures surrounding the emerging left trigeminal nerve was thinned, presumably 76 secondary to pressure atrophy. The nerve was iso- to hypointense to grey matter on T1W, 77  5 T2W FSE, and 3D-SPGR and exhibited heterogeneous, mainly peripheral enhancement on 78 T1W sequence after contrast administration (Fig. 1). The imaging findings were consistent 79 with an extensive, diffuse left trigeminal neuropathy. The main differential diagnosis was 80 a peripheral nerve sheath tumor. Cerebrospinal fluid was collected from the 81 cerebellomedullary cistern and the analysis (nucleated cell count, total protein, and 82 cytology) was within normal limits. 83  84 Ultrasonographic examination (Philips HDI 5000, Bothell, USA) of the infraorbital nerve 85 at its exit from the infraorbital canal was performed using a 8.5 MHz microconvex array 86 transducer and 12 MHz linear array transducer in order to obtain a fine needle aspirate or 87 tru-cut biopsy; however, the nerve did not appear abnormal at this level precluding non-88 invasive sampling. 89  90 The ulcer initially improved with evidence of healing and epithelialisation but then rapidly 91 progressed to a large descematocoele requiring either surgical repair or enucleation. Given 92 the poor prognosis the owner declined any further treatment and elected to have the horse 93 euthanized. Post mortem examination confirmed gross enlargement of the left orbital 94 fissure, round foramen, and infraorbital canal in addition to the ophthalmic and maxillary 95 branches of left CN V (Fig. 2). Histopathology revealed that the trigeminal nerve was 96 markedly expanded by a densely cellular population of fibroblasts arranged in parallel 97 bundles depositing moderate amounts of fibrillar eosinophilic matrix. Admixed were large 98 numbers of infiltrating macrophages, lymphocytes, plasma cells, neutrophils, 99 multinucleated giant cells and eosinophils. Inflammatory cells are focused upon nerve 100  6 fascicles, with rupture of the perineurium and extension of inflammatory cells into the 101 interfascicular interstitium (Fig. 3). There was marked myelin degeneration with associated 102 axonal swelling (spheroids). The left infraorbital nerve at its exit from the infraorbital 103 canal, which was accessible to ultrasound examination, appeared mildly enlarged. 104 Histopathology at the same level revealed an extensive expansion of the fibrous connective 105 tissue surrounding the nerve fascicles, with small aggregates of lymphocytes. All these 106 findings were consistent with a severe granulomatous neuritis affecting the ophthalmic and 107 maxillary branches of the left trigeminal nerve.  108  109 Discussion 110 The etiology of the progressive granulomatous inflammation of the left trigeminal nerve in 111 this case remains undetermined. Granulomatous inflammation affecting the cranial nerves 112 has been associated with polyneuritis equi (PNE);1 however, clinical experience has 113 suggested that horses with PNE presenting primarily with cranial nerve deficits eventually 114 also show cauda equina deficits.2 Moreover, the most common clinical signs reported when 115 the cranial nerves are involved include atrophy of the muscles of mastication, dysphagia, 116 head tilt, facial nerve paresis and head shaking.3-6 In the present case, the neurological 117 examination did not reveal involvement of any other cranial nerve or any signs of cauda 118 equina dysfunction (poor tail tone, faecal and urinary incontinence, pelvic limb weakness 119 or pelvic limb muscle atrophy) at the time of presentation. However, a subclinical PNE 120 affecting this area could not be ruled out because the cauda equina was not assessed on 121 post-mortem examination. The underlying cause of PNE remains unknown, but an 122  7 underlying immune-mediated process has been suggested.5,7 Corticosteroids and 123 azathioprine have been proposed as potential treatments to slow progression of the disease.4 124  125 The MR imaging features of peripheral nerve sheath tumor (PNST) affecting the cranial 126 nerves have not been described in horses. There is a case report of lingual PNST in a horse, 127 where MR imaging revealed a large, round, well defined and encapsulated mass with mixed 128 signal intensity on T2W and T1W images.8 Some consistent, although nonspecific, MR 129 imaging features of PNST in dogs include diffuse thickening of the nerve that is typically 130 iso to hyperintense on T2W FSE sequences and iso-to hypointense on T1W FSE sequences 131 to normal muscle with heterogeneous contrast enhancement.9,10 Similar findings in our 132 case, together with the chronicity of the changes and degree of enlargement, suggested an 133 ante-mortem diagnosis of PNST; however, histopathology confirmed a severe 134 granulomatous neuritis.  135  136 There is a report of a trigeminal nerve sarcoid granuloma mimicking a trigeminal PNST in 137 a person.11 This case had a similar expansile mass of the trigeminal nerve and was thought 138 to be a PNST; however, histopathology confirmed a sarcoid granuloma. Equine sarcoids 139 are attributed to non-productive infection with bovine papillomavirus.12,13 Histopathology 140 typically reveals fibroblast proliferation with spindle cells often arranged in bundles, oval 141 nuclei and small nucleoli. Peripheral nerve sheath tumor can histologically be difficult to 142 distinguish from sarcoids. Differentiation can be made with immunohistochemistry 143 staining for S-100 protein.14 However, histopathology in the present case was not consistent 144 with sarcoid granuloma. 145  8  146 The MR imaging findings in this horse confirmed the clinical diagnosis of trigeminal 147 neuropathy and led clinicians to consider the possibility of further investigating the area of 148 the affected nerve to reach a final diagnosis. On ultrasonographic examination the 149 infraorbital nerve appeared normal at its exit from the infraorbital canal. Given the normal 150 appearance of the nerve, fine needle aspiration was not attempted. Nevertheless, post-151 mortem examination of the nerve at this level revealed some abnormalities and fine needle 152 aspiration or a surgical biopsy could have provided more diagnostic information than 153 anticipated. 154  155 In conclusion, granulomatous neuritis should be considered as a differential diagnosis in 156 horses with MR imaging findings suggestive of a trigeminal nerve sheath tumor. These 157 inflammatory changes can result in severe enlargement of the nerve mimicking a nerve 158 sheath tumor. Therefore, a surgical biopsy may be indicated to further characterize these 159 lesions in order to plan the best treatment approach. 160  9 References 161  162 1. Cummings JF, de Lahunta A, Timoney JF. Neuritis of the cauda equina, a chronic 163 idiopathic polyradiculoneuritis in the horse. Acta Neuropathol. 1979;46:17–24. 164 2. Bazargani T, Rafia S, Helan JAH, Moaddab SH. Occurrence of Unilateral Posterior 165 Polyneuritis in an 8-year-old Crossbred Mare. J Equine Vet Sci 2010; 30:711–714.  166 3. Hahn CN. Miscellaneous Disorders of the Equine Nervous System: Horner’s 167 Syndrome and Polyneuritis Equi. Clin Tech Equine Pract 2006;5:43–48.  168 4.  Aleman M. Miscellaneous neurologic or neuromuscular disorders in horses. Vet 169 Clin North Am Equine Pract 2011;27:481-506. 170 5. Van Galen G1, Cassart D, Sandersen C, Delguste C, Nollet H, Amory H, Ducatelle 171 R. The composition of the inflammatory infiltrate in three cases of polyneuritis equi. 172 Equine Vet J 2008;40:185-188. 173 6. Roberts VL1, Perkins JD, Skärlina E, Gorvy DA, Tremaine WH, Williams A, 174 McKane SA, White I, Knottenbelt DC. Caudal anaesthesia of the infraorbital nerve 175 for diagnosis of idiopathic headshaking and caudal compression of the infraorbital 176 nerve for its treatment, in 58 horses. Equine Vet J. 2013;45:107-110.  177 7.  Aleman M, Katzman SA, Vaughan B, Hodges J, Crabbs TA, Christopher MM, 178 Shelton GD, Higgins RJ. Antemortem diagnosis of polyneuritis equi. J Vet Intern 179 Med 2009;23:665-668. 180 8. A. Schneider, C. Tessier, D. Gorgas, P. Kircher, J. Mamani, J. Miclard. Magnetic 181 resonance imaging features of a benign peripheral nerve sheath tumour with 182 ‘ancient’ changes in the tongue of a horse. Equine Equine Veterinary Educ 183 2010;22:346–351. 184 9. Kraft S, Ehrhart EJ, Gall D, et al. Magnetic resonance imaging characteristics of 185 peripheral nerve sheath tumors of the canine brachial plexus in 18 dogs. Vet Radiol 186 Ultrasound 2007;48:1–7.  187 10. Davis EG, Coates JR, Johnson GC, Cook CR, Pardo ID. What is your neurologic 188 diagnosis? Peripheral nerve sheath tumor. J Am Vet Med Assoc 2011;239:189–191. 189 11.  Quinones-Hinojosa A, Chang EF, Khan SA, McDermott MW. Isolated trigeminal 190 nerve sarcoid granuloma mimicking trigeminal schwannoma: case report. 191 Neurosurgery 2003;52:700-705. 192 12. Otten N, von Tscharner C, Lazary S, Antczak DF, Gerber H. 1993. DNA of bovine 193 papillomavirus type 1 and 2 in equine sarcoids: PCR detection and direct 194 sequencing. Arch. Virol. 132:121–131. 195  10 13 Lunardi M1, de Alcântara BK, Otonel RA, Rodrigues WB, Alfieri AF, Alfieri AA. 196 Bovine papillomavirus type 13 DNA in equine sarcoids. J Clin Microbiol. 197 2013;51:2167-2171. 198 14. Bogaert L1, Heerden MV, Cock HE, Martens A, Chiers K. Molecular and 199 immunohistochemical distinction of equine sarcoid from schwannoma. Vet Pathol. 200 2011;48:737-741. 201  202 203  11 Figure captions 204  205 Figure 1 (A) Transverse T1-weighted (T1W) image at the level of the orbital fissure. 206 (B) Transverse T1W image after contrast administration at the same level 207 of Fig 1A. (C) Dorsal T1W image after contrast administration (TR=520ms, 208 TE=15.5ms, slice thickness 5mm). There is enlargement of the ophthalmic 209 and maxillary branches of the left trigeminal nerve from the level of middle 210 cranial fossa, through the orbital fissure and round foramen respectively. 211 The infraorbital branch of the maxillary branch of the trigeminal nerve is 212 markedly enlarged along the length of the infraorbital canal (arrow) (C). 213 The nerve was iso- to hypointense to grey matter on T1W (A) with 214 heterogeneous, mainly peripheral enhancement on T1W sequence (B) after 215 contrast administration. There was bony remodelling and secondary 216 enlargement of the left orbital fissure (arrow) (A,B). 217  218   219  12 Figure 2 View of the inner cranial vault after removal of the brain. Gross enlargement 220 of left orbital fissure and round foramen is visible (arrow). The ophthalmic 221 and maxillary branches of left trigeminal nerve (black asterisk) are enlarged 222 compared to the right trigeminal nerve (white asterisk). 223  224   225  13 Figure 3 Histopathology from a section of the left trigeminal nerve from the affected 226 horse (original magnification x 40 (A) and x 200 (B)). Haematoxylin and 227 eosin showed revealed that the trigeminal nerve was markedly expanded by 228 a densely cellular population of fibroblasts arranged in parallel bundles 229 depositing moderate amounts of fibrillar eosinophilic matrix. Admixed 230 were large numbers of infiltrating macrophages, lymphocytes, plasma cells, 231 neutrophils, multinucleated giant cells and eosinophils. Proliferation of 232 fibroblasts, and associated deposition of collagen, has resulted in marked 233 thickening of the perineurium. A densely cellular infiltrate is observed, 234 extending into the nerve fascicles through the endoneurium.  This infiltrate 235 is composed of lymphocytes, plasma cells, macrophages, multinucleated 236 giant cells, and small numbers of eosinophils.  Leukocytic infiltration is 237 associated here with neuronal destruction. 238  239 

Imaging diagnosis - unilateral trigeminal neuritis mimicking peripheral nerve sheath tumor in a horse

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Imaging diagnosis - unilateral trigeminal neuritis mimicking peripheral nerve sheath tumor in a horse

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