Radial Nerve Paralysis in a Newborn Quarter Horse Foal

Stephen B. Miletta DVM, cVMA

Abstract: A newborn Quarter Horse foal presented for radial nerve paralysis with dropped elbow in the right front limb.  Initial treatment at a referral facility included: splint management, stall rest, passive range of motion (PROM) and non-steroidal anti-inflammatory drugs (NSAIDS). After discharge, three treatments of acupuncture and electroacupuncture were performed, after which the patient was able to extend the limb normally and not drag her toe.

History: A Quarter Horse filly born on 7/8/2023 was found to have right front radial nerve paralysis with inability to extend the elbow, carpus, and digit. The birth occurred in a stall with no outward signs of trauma to the foal or mare and radiographs were negative for fractures.  The veterinarian and owners decided to send the foal to a referral facility for initial splint management, PROM, toe extension and NSAIDS. After 6 weeks, the foal was discharged, and some improvement was noted but radial nerve paralysis was still present to include dropped elbow, tripping and failure to extend the limb normally (see video). First examination and medical acupuncture treatment started on 9/6/2023.

Physical Exam: A lameness grade was assigned using the American Association of Equine Practitioners lameness scale (0-5, where 0= no lameness, 1= is difficult to observe and is not consistently apparent, regardless of circumstances, 2= lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances, 3=lameness is consistently observable at a trot under all circumstances, 4= lameness is obvious at a walk, 5= lameness produces minimal weight bearing in motion or at rest or results in complete inability to move)1. Lameness exam grade 4-5/5 on the right front on 9/6/2023.  At rest the right front limb exhibited a dropped elbow, with weakness of the extensor and triceps muscles. During locomotion the patient was unable to normally extend the limb resulting in toe dragging and flexing of the carpal and metacarpophalangeal joints. This repetitive trauma caused abrasion of the epidermis on the dorsal metacarpophalangeal joint and pastern region requiring a protective bandage.  Deep pain was present and normal in the distal limb. Myofascial exam- distal cervical tenderness on palpation over the brachiocephalicus muscles near ST 10 and LI 16 with decreased muscle tone in the right triceps region.  Normal tone over the supraspinatus and infraspinatus muscles was present in the right shoulder region.

Problem List: Right front radial nerve paralysis with dropped elbow, failure to extend limb, knuckling over at the metacarpophalangeal joint and muscle weakness.

 Differential Diagnoses: Radial nerve paralysis differential diagnoses include: trauma, humeral fracture, brachial plexus injury, neoplasia, dystocia and prolonged lateral recumbency2.

Diagnosis: Compression trauma from parturition resulting in radial nerve paralysis.

 Medical Decision-making: The radial nerve innervates the triceps muscle and the extensor muscles of the front limb. It is part of the brachial plexus that originates from the ventral rami of C6-T2 spinal segments3. Primary focus of treatment is to stimulate nerve activity, promote nerve repair4 and neuromodulation through the points that influence the radial nerve using dry needling and electroacupuncture. Specifically, the caudal cervical and thoracic segments that give rise to the brachial plexus.

Medical Acupuncture Specifics:

  1. 9/6/2023 for the first treatment dry needling with Blue Seirin J 0.20×30 mm needles placed on R side at LI 11, LI 16, LI 17, SI 11, SI 12, ST 10 for 15 minutes.
  2. 9/12/2023 for the second treatment Carbo 0.25×30 mm needles placed on the R side at LI 6, LI 7, LI 10, LI 16, SI 9, SI 11, SI 12, LU 1 for 20 minutes total as she tolerated it well. Electroacupuncture was done for 10-15 of the 20 minutes (had to replace some points as they came out from patient movement), between LI 6 to LI 16 and SI 9 to SI 12 @ 20 Hz using the ITO ES-130.
  3. 10/5/2023 for the third treatment Carbo 0.25×30 mm needles placed on the R side at LI 7, LI 10, LI 16, SI 11, SI 12, ST 10, LU 1. Electroacupuncture was done for 15 of the 20 minutes (had to replace some points as they came out from patient movement), between LI 10 to LI 16 and SI 11 to SI 12 at 20 Hz using the ITO ES-130.

Outcomes, Insights, Discussion: Between the first and second treatments the patient made significant improvement in her extensor muscle tone resulting in greater limb extension and decrease in lameness score to a grade 3-4/5.  The Seirin J coated needles went in easily and were well tolerated but tended to work out as the foal stood. Switching to the uncoated Carbo needles helped with needle grab and retention for the second and third treatments. Sedation was also required after the first treatment as she was getting physically stronger and harder to restrain. On the day of the third treatment the patient was walking more normal, rarely exhibiting a slight toe drag and had a lameness score of grade 1-2/5. The original plan was to treat every week but due to scheduling conflicts the third treatment was about 3 weeks from the second. After the third treatment it was decided to discontinue due to her recovery and overall positive response to acupuncture, with the limb returning to normal function and a grade 0/5 lameness.

References:

  1. American Association of Equine Practitioners. Lameness Exams: Evaluating the Lame Horse. AAEP Lameness scale. Available at: https://aaep.org/horsehealth/lameness-exams-evaluating-lame-horse
  2. MacKay Robert. Diseases of the Peripheral Nerves, Neuromuscular Junction, or Uncertain Sites: Relevant Examination Techniques and Illustrative Video Segments. AAEP Proceedings 2011; 57:363-366.
  3. Levine Jonathan, Levine Gwendolyn, Hoffman Anton, et al: Comparative Anatomy of the Horse, Ox, and Dog: The Vertebral Column and Peripheral Nerves. Compendium Equine 279-292, September/October 2007.
  4. Liu YP, Luo ZR, Wang C, Cai H, Zhao TT, Li H, Shao SJ, Guo HD. Electroacupuncture Promoted Nerve Repair After Peripheral Nerve Injury by Regulating miR-1b and Its Target Brain-Derived Neurotrophic Factor. Front Neurosci. 2020 Sep 29; 14:525144. doi: 10.3389/fnins.2020.525144. PMID: 33132818; PMCID: PMC7550428.