Determining the cause of neurologic signs in neonates

A closer look at genetics is offering new insight into disease conditions.
Jul 01, 2010

Q: Please provide an update on neonatal and genetic testing in puppies.

A: Dennis O'Brien, DVM, gave an excellent lecture titled "Neonatal neurology: Assessing the runt" at the 2009 American College of Veterinary Internal Medicine Forum in Montreal, Canada. O'Brien is professor of neurology at the University of Missouri's College of Veterinary Medicine. Some relevant points in this lecture are provided in this column.

Neonatal diseases have received relatively little attention in veterinary medicine. Most ill neonates are dismissed as runts or as "fading," and little effort is put into identifying the underlying cause. With the advent of genomics, the genetics of many hereditary diseases are being elucidated, allowing for disease prevention through DNA testing. Breeders want to decrease the incidence of these diseases both to improve the health of their breed and to improve their bottom line. Precise characterization of neonatal diseases defines syndromes and, in the case of genetic disorders, can provide clues to the underlying genes responsible.

Development and neurologic examination of the neonate

Recognizing and localizing neurologic lesions in neonates is difficult because their nervous systems are undergoing rapid changes during development. For example, crossed extension, which is a sign of upper motor neuron disease in an adult, is normal during the first few weeks of life.

Table 1
When assessing a neonatal patient, record the animal's precise age, and consider the stage of development when interpreting behavior and neurologic examination findings. Table 1 outlines the different stages of early development and the corresponding behaviors and key elements of neurologic development. Approximate ages for the developmental milestones are given based on experimental observations with limited breeds represented. Note that breed variations are the rule rather than the exception, but these age ranges provide some guidance as to whether an individual is delayed.

As mentioned previously, components of the neurologic examination will change with development.