How to Perform a Neurological Exam for Pets

A patient’s mental status is evaluated through observation in the exam room, in addition to any history provided by the pet parent. A normal pet will be alert and responsive to the environment and the people in the room, while a neurologic pet may range from dull to comatose. The severity of the mentation will also help us understand where the lesion is located. For example, brainstem lesions cause more severe mentation changes.

When assessing gait and posture, first determine whether the patient is ambulatory (can walk) or non-ambulatory (cannot walk). Next, establish which limbs are affected and to what degree (ataxia vs. paresis vs. plegia). And finally, look for any postural abnormalities (head tilt or head turn).

There are three types of ataxia (incoordination). A patient that is unable to walk a straight line or that walks in a crisscross fashion would indicate proprioceptive ataxia. A patient that has balance issues, appearing “drunk” or falling over to one side, would have vestibular ataxia. In contrast, cerebellar ataxia would present with over-exaggerated movements or tremors.

Paresis (reduced motor function) and plegia (paralysis) can occur in one limb (mono), both back legs (para), or all 4 limbs (tetra). If a patient is determined to be plegic, it is critical for prognosis to check for sensation in the affected limbs by pinching the toes with hemostats.

Cranial nerves are responsible for smell; vision and eye movement; facial movements; hearing and balance; and chewing, swallowing, barking, and tongue movement. Evaluating the responses of some of these nerves helps localize the damage.

• Menace Response (Cranial Nerves II, VII)
  Covering one of the patient’s eyes with one hand while bringing the other hand toward the patient’s other eye should cause the pet to blink.
• Pupillary Light Reflex (Cranial Nerves II, III)
  Shining a bright light into one of the patient’s eyes should cause that pupil to contract (Direct PLR) and consequentially, the other pupil to contract (Consensual PLR).
• Nasal Sensation (Cranial Nerve V)
  Touching the nasal mucosa just inside the nose should cause the patient to pull away.
• Muscle of Mastication (Cranial Nerve V)
  Observe the patient’s head and face for muscle symmetry. For our fluffier friends, touch the head and face to feel for the symmetry.
• Palpebral Reflex (Cranial Nerves V, VII)
  Touching the medial and lateral canthus (inner and outer corners) of the patient’s eyes should cause the pet to close them.
• Physiologic Nystagmus (Cranial Nerves III, IV, VI)
  When moving the patient’s head from left to right and up and down, the pet’s eyes should follow along in the same direction and stop once the end position is reached, without any additional eye movements.
• Spontaneous and Positional Nystagmus (Cranial Nerve VIII)
  Observe the patient for abnormal eye movement patterns while at rest and also when the head is positioned a certain way. If present, also note the fast phase direction (the direction the eyes dart before snapping back).
• Resting and Positional Strabismus (Cranial Nerves III, IV, VI, VIII)
  Observe the patient for asymmetrical eye alignment while at rest and also when the head is positioned a certain way. If present, note the direction that the misaligned eye points.
• Jaw Tone (Cranial Nerve V)
  Open the patient’s mouth to observe jaw tone.
• Gag Reflex (Cranial Nerves IX, X)
  With a docile pet, open the patient’s mouth and insert a finger toward the back of the larynx. With a less cooperative pet, gently press around the larynx externally to initiate a swallow.
• Tongue Strength/Symmetry (Cranial Nerve XII)
  Use food to make the patient lick its nose to assess the tongue for strength. Open the patient’s mouth to observe the tongue’s symmetry.

Testing whether or not the patient understands where its limbs are in space and whether or not the patient can maintain a normal upright position is important to uncover subtle postural deficits that may not be noticeable during gait and posture analysis.

• Standing Paw Placements
  Support the patient’s body weight and knuckle over each paw, observing whether or not the pet can appropriately replace it.
• Hopping
  Take away three legs, and observe whether or not the patient can hop on one leg laterally.
• Hemiwalking
  Take away both limbs from the same side, pushing the patient toward the other side, and observe whether or not the pet can hop laterally on the other two limbs.
• Wheel Barrowing
  Take away both back limbs, pushing the patient forward, and observe whether or not the pet can walk on the two front limbs.
• Extensor Postural Thrust
  Lift the patient up and set back down on rear limbs, observing whether or not the back legs scoot back underneath the pet.

The most reliable reflexes for achieving lesion localization are the flexor withdrawal and patellar reflexes.

• Thoracic and Pelvic Limb Withdrawal Reflex
  Pinching the webbing between the toes should cause the patient to flex and bring that limb all the way back. Also note whether or not the opposite limb compensates for the loss of support (crossed extensor).
• Patellar Reflex
  Holding a pelvic limb up with the knee slightly flexed and hitting the patellar tendon with a reflex hammer should cause the patient to extend the stifle.
• Cutaneous Trunci
  Pinching along the wings of the ilium over the hips should cause the patient’s skin to twitch along both sides.
• Perineal Reflex
  Gently passing hemostats externally around the anus should cause the patient’s sphincter to contract.

Palpate down the length of the spinal column testing for pain or discomfort, and then test the head and neck for range of motion. And remember, if the patient is plegic, it’s critical for prognosis that the affected limbs are assessed for pain sensation (nociception) by pinching the toes with hemostats.