Diagnosing and Treating Avian Neurologic Disease

Key Points

  • Understand avian anatomic variations in cranial and spinal nerve anatomy. The avian spinal cord extends the entire length of the vertebral column, and there is no cauda equina. The number of spinal nerves in the bird depends on the number of vertebrae.
  • Although the avian neurologic examination varies little from that of the mammal, assessment can be challenging.
  • Serial neurologic assessment aids in establishing diagnosis and prognosis.
  • Neurologic patients require rapid intervention, frequent assessment, and often intensive care.
  • Seizures are a common neurologic problem that may arise from many etiologies. Important differential diagnoses include renal disease or renal failure, hypocalcemia, hypoglycemia, hyperlipemic syndrome, proventricular dilatation disease, psittacosis, atherosclerosis, and lead toxicity. It is unclear whether hepatic encephalopathy truly occurs in birds since nitrogenous waste is not the end product of hepatic metabolism.

The cranial nerve exam differs little from that of mammals, however there are differences in innervation. As in mammals, menace and pupillary light response (PLR) require use of cranial nerves II (optic) and III (oculomotor), however menace is difficult to interpret in birds. Also, PLR may be overridden in birds due to the presence of striated iridal muscle. Evaluate PLR early in the exam using a sudden, bright light directed toward the medial canthus. Consensual PLR is absent due to . . .


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References

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Bennett RA. Neurology. In: Ritchie BW, Harrison GJ, Harrison LR (eds). Avian Medicine: Principles and Application. Lake Worth, FL: Wingers Publishing; 1994: 728-747.

Benzo CA. Nervous system. In: Sturkie PD (ed). Avian Physiology, 4th ed. New York, NY: Springer-Verlag; 1986:1-36.

Clippinger TL, Bennet RA, Platt SR. The avian neurologic examination and ancillary neurodiagnostic techniques. J Avian Med Surg 10(4):221-247, 1996.

Jones MP, Orosz SE. Overview of avian neurology and neurological disease. Semin Avian Exotic Pet Med. 5(3):150-164, 1996.

King AS, McLelland J. Nervous system. In: King AS, McLelland J (eds). Birds: Their Structure and Function, 2nd ed. London, UK: Balliere Tindall; 1984:237-283.

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Oliver JE, Lorenz MD. Handbook of Veterinary Neurologic Diagnosis, 2nd ed. Philadelphia, PA: WB Saunders, 1993.

Orosz SE. Principles of avian clinical neuroanatomy. Semin Avian Exotic Pet Med. 5(3):127-139, 1996.

Plumb DC. Veterinary Drug Handbook, 4th ed. Ames, IA: Iowa State University Press; 2002.