A 10-year-old Native American girl from northern New Mexico presented with a 5-month history of intermittent neck, right arm, and shoulder pain with progressive right arm weakness. Approximately one month prior to admission, she developed left leg weakness causing multiple falls weekly, progressive visual changes, and aphasia. The girl was afebrile and well appearing. She demonstrated weakness in her right deltoid, bicep, and hand. Right-sided pronator drift, Hoffmann's reflex and Babinski's reflex, and narrow-based gait were noted. No skin nodules were seen. Her peripheral white blood cell count was 14.8 cells x 103/muL, with 88% polymorphonuclear cells, 9% lymphocytes, and 3% monocytes.
Contrasted magnetic resonance imaging (MRI) of the brain was unremarkable. A contrasted MRI scan of the cervical spine revealed a 2.8 cm anterior intradural, extramedullary enhancing mass without restricted diffusion. A dural tail, centered at the level of the fifth cervical vertebra, was present, with enhancement and cord compression (Figure 1). Angiography demonstrated patent major cervical arteries. Testing for tuberculosis, Coccidioides immitis, Bartonella henselae, Histoplasma spp., and Cryptococcus spp. was negative. A chest X-ray scan was unremarkable. C-reactive protein, erythrocyte sedimentation rate, and lumbar puncture were not obtained at admission.
The patient underwent resection of the mass, with resultant anterior C5 and C6 corpectomies, C4-C5 and C6-C7 discectomies, and C4-C7 arthrodesis. The lesion was extremely adherent to the dura, requiring dissection and mobilization from the nerve root and spinal cord. Histopathology demonstrated fibrous tissue with caseating granulomas, with negative Fite's, Grocott-Gomori methenamine silver (GMS), and Gram stains. On postoperative day nine, a large pseudomeningocele developed in the neck, which improved following insertion of a lumbar drain.
The patient resided in an area likely endemic for O. lupi. Black flies of the Simulium genus reside in the state along the Rio Grande river, with increased numbers noted during warm weather months. However, our patient denied exposure to putative risk factors for this infection (no exposure to bodies of freshwater, to areas where there are dogs with ocular disease, or to black fly bites). Initially, no helminth was seen, but a tissue specimen was sent to the Centers for Disease Control and Prevention. Fragments of inflamed, dense fibrous connective tissue contained abundant granulomas with irregular borders and areas of central necrosis. Intervening stroma contained strands of inflammatory infiltrates comprising plasma cells and macrophages, admixed with hemorrhage and occasional eosinophils. Within a few fragments of tissue were remnants of foreign material compatible with the cuticular wall of a degenerating nematode (Figure 2), for which morphological details could be emphasized using a trichrome stain. The outer cuticular ridges were dome-shaped and consistent with filariae in the genus Onchocerca. Other features typical of Onchocerca spp. that were evident included a thick hypodermis, weakly developed muscle cells rather vacuolated in appearance, and broad lateral chords. Longitudinal sections of the cuticular wall revealed two inner striae per ridge, morphologically compatible with O. lupi, likely damaged by host immune response (Figure 3). No microfilariae were identified. The polymerase chain reaction test of these anatomic specimens definitively confirmed the species' identity as O. lupi.
The patient was treated with a single dose of ivermectin (12 mg), followed one week later by a six-week course of doxycycline (200 mg once daily). After completing a 26-day hospital stay (with 21 days postoperatively in the pediatric intensive care unit), she was discharged with slightly decreased strength in her right arm. She returned to a normal neurological examination at a two-month follow-up visit in the infectious disease clinic. A contrasted MRI scan and plain films of the cervical spine five months after discharge revealed only postsurgical changes.