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Degeneration of Axenfeld nerve loop: a clinicopathologic case report

      Axenfeld
      Axenfeld
      Ueber intrasklerale Nevenschleifen.
      first reported intrascleral nerve loops of the long ciliary nerve, now known as Axenfeld nerve loops, in 1902. A nerve loop extends through the sclera to the external surface.
      Axenfeld
      Ueber intrasklerale Nevenschleifen.
      Reese
      • Reese A.B.
      Intrascleral nerve loops.
      reported that about 65% of these patients show neuroma-like enlargement of the cupola and the loop can be pigmented at its scleral entry. Therefore, an Axenfeld nerve loop could be confused with a nevus, tumour, or foreign body.
      • Reese A.B.
      Intrascleral nerve loops.
      • Katz D.
      Intrascleral nerve loops.
      • Crandall A.S.
      • Yanoff M.
      • Schaffer D.B.
      Intrascleral nerve loop mistakenly identified as a foreign body.
      Axenfeld nerve loops are common, but enlargement of a nerve loop has not been reported, to our knowledge. We report a rare case of an Axenfeld nerve loop that grew larger.
      A 61-year-old female had a nontender, smooth, oval, well-circumscribed, subconjunctival nodular lesion associated with tortuous episcleral vessels, which was found accidentally. She had no previous ocular operation or history of trauma. On slit-lamp examination, the episcleral mass, measuring 1.6 × 1.2 mm in surface dimensions, was located approximately 3 mm from the limbus in the inferonasal quadrant. The base of the lesion seemed to be adherent to the sclera and free from the conjunctiva. Five months later, slight enlargement of the mass was observed (1.8 × 1.5 mm) (Fig. 1B). With the patient’s consent, an excisional biopsy of the mass was performed. We found a large scleral hole and the episcleral mass was connected to the internal tissue through this hole. Although the external portion of the lesion was a well-encapsulated, semisolid mass, the internal portion seemed to be mucoid and soft tissue with dark pigment (Fig. 1A). After excising it, we closed the scleral hole to prevent the uveal tissue from protruding. The postoperative course was uncomplicated. A biopsy was taken of the lesion, and microscopic examination of histologic sections revealed nerve bundles with cleft formation and interstitial myxomucoid degeneration (Fig. 1C–F). Most of the cells were strongly positive for S-100 protein (Fig. 1G).
      Figure thumbnail gr1
      Fig. 1Clinical photograph (A, B) and staining (C–F). A, Microscopic appearance of the episcleral mass. External (arrowhead) and internal (arrow) portions of the lesion. C–F, Histologic sections showed hypertrophic peripheral nerve bundles with dark pigment, cleft formation, and interstitial myxomucoid degeneration (hematoxylin and eosin staining). G, Most of the cells were strongly positive for S-100 protein (immunohistochemical staining for S-100 protein). Original magnification ×100 (C, D, G), ×400 (E, F).
      In general, Axenfeld nerve loops do not require treatment.
      • Reese A.B.
      Intrascleral nerve loops.
      However, the enlarging and painless nature of the mass in our patient was atypical, although the location of the lesion was consistent with an Axenfeld nerve loop. Chang and Glasgow
      • Chang H.S.
      • Glasgow B.J.
      Evidence that anterior episcleral nerve sheath tumors arise from the Axenfeld nerve loop.
      suggested that most anterior scleral nerve sheath tumours arise from Axenfeld nerve loops. In this case, an excisional biopsy of the mass was performed because the lesion was becoming larger. A histopathologic study is necessary to distinguish between an Axenfeld nerve loop and a tumour, such as a schwannoma or neurofibroma. The excisional biopsy revealed nerve bundles with cleft formation and interstitial myxomucoid degeneration. Compression and stretching of the long ciliary nerve by repetitive eyelid movements, such as blinking and rubbing, might result in this form of nerve degeneration, as suggested by Hashimoto et al.,
      • Hashimoto T.
      • Hamada T.
      • Nakamura T.
      • Sasaguri Y.
      • Suzuki K.
      Myxoid and globular degeneration of nerves in the shoulder joint.
      who reported myxoid degeneration of the axillary nerve in the shoulder joints. We assumed that after the initial protrusion of the nerve cupola, the ensuing pressure exacerbated the protrusion and facilitated abnormal degeneration of the ciliary nerve.
      We report a rare case of an enlarging Axenfeld nerve loop that showed abnormal degeneration of the ciliary nerve. When such a nodule is found to be progressively enlarging, surgical excision may be required to rule out other tumours.

      References

        • Axenfeld
        Ueber intrasklerale Nevenschleifen.
        Ber Dtsch Ophthalmol Ges. 1902; 30: 134-137
        • Reese A.B.
        Intrascleral nerve loops.
        Trans Am Ophthalmol Soc. 1931; 29: 148-153
        • Katz D.
        Intrascleral nerve loops.
        Indian J Ophthalmol. 1971; 19: 2-6
        • Crandall A.S.
        • Yanoff M.
        • Schaffer D.B.
        Intrascleral nerve loop mistakenly identified as a foreign body.
        Arch Ophthalmol. 1977; 95: 497-498
        • Chang H.S.
        • Glasgow B.J.
        Evidence that anterior episcleral nerve sheath tumors arise from the Axenfeld nerve loop.
        Arch Ophthalmol. 2009; 127: 1060-1062
        • Hashimoto T.
        • Hamada T.
        • Nakamura T.
        • Sasaguri Y.
        • Suzuki K.
        Myxoid and globular degeneration of nerves in the shoulder joint.
        Clin Orthop Relat Res. 1995; 320: 55-64