Neurological Examination and Diagnostic Testing in Birds and Reptiles
Neurological Examination and Diagnostic Testing in Birds and Reptiles
Neurological Examination and Diagnostic Testing in Birds and Reptiles
Abstract
Neurological dysfunction is a frequently presenting sign in avian and reptile patients. Clinical neurological signs are rarely pathognomonic, often requiring the attending veterinary surgeon to perform more
involved diagnostic tests to achieve a diagnosis. Variations in patient anatomy, physiology and
demeanour present unique challenges to the veterinarian evaluating the bird or reptile that has
neurological disease signs. Despite these challenges, a well-structured physical and neurological
examination can often be accomplished with minimal equipment. A structured neurological examination
is essential to formulate an appropriate investigative plan and therapeutic regime for these difcult cases
and to provide the owner with an accurate prognosis. Copyright 2014 Elsevier Inc. All rights reserved.
Key words: avian; examination; neurological; reex; reptile
basic knowledge of the normal anatomy and physiology of the reptile and avian nervous
system is essential to enable the veterinary clinician to accurately diagnose neurological
disease in these animals.1-14 Variations in anatomy, physiology, temperament, and
tolerance to handling between the various avian and reptile species can make the
neurological examination and localisation of lesions challenging in these patients. Reptiles,
being ectothermic, have reexes that are inuenced by body temperature; therefore, reptiles should be
examined in an environment that is within their selected body temperature range.
Although there are few exceptions, the
neuroanatomy of reptiles and birds is similar to
mammals, and the neurological examination may
be approached in a similar manner to that
described for dogs and cats.15 Naturally some
modications may be required when performing a
neurological examination on a bird or reptile
patient owing to differences in anatomy and
temperament.
Neurological disease signs in birds and reptiles
are often nonspecic, consequently a disease
diagnosis using external clinical signs alone is
rarely achieved. Birds and reptiles mask illness, or
owners are unaware of subtle disease signs until
well advanced, resulting in many of these patients
being presented to the veterinary clinic in a critical
disease state. These critical presentations, with
often one or more life-threatening disease
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Pen torch
Hypodermic needles
Mosquito forceps
Towel
Gloves
Perch
Digital thermometer
Mouth gags
Cotton-tipped applicators
TABLE 2. Avian cranial nerves and their function and clinical tests to determine normal function and clinical
signs of dysfunction
Nerve
I Olfactory
Sensoryolfaction
II Optic
Sensoryvision
III Oculomotor
Motorextrinsic ocular
muscles and upper
eyelid muscle
Parasympathetic
intrinsic ocular muscle
IV Trochlear
V Trigeminal:
Ophthalmic branch
Maxillary branch
Mandibular branch
VI Abducens
VII Facial
VIII Vestibulocochlear
IXa Glossopharyngeal
Xa Vagus
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Function
Motorextrinsic ocular
muscle
Sensory (upper lid,
forehead skin, nasal
cavity and upper beak)
Sensory (both lids, hard
palate, nasal cavity
and lateral upper
beak)
Motor (orbicularis, lower
lid and chewing)
Sensory (lower beak skin
commissures)
Motorextrinsic ocular
muscles and nictitans
Motorfacial expression
Sensorytaste
Parasympatheticmost
glands of the head
Sensoryhearing
Sensorybalance and
coordination
Sensorytaste and
sensation in the
tongue and trachea
Motorpharynx, larynx,
crop and syrinx
Sensorylarynx, pharynx
and viscera
Motorlarynx, pharynx,
oesophagus and crop
Clinical Test
Sign of Dysfunction
Dilated pupil
Dorsolateral deviation
Response to touch,
palpebral reex
Lack of sensation
Unable to blink
Menace reex
Medial deviation
Nictitans immobility
Facial asymmetry
Poor taste
Decreased secretions
Response to sound
Oculocephalic reex
Righting reex
Gag reex
No response to sound,
head tilt, nystagmus,
abnormal posture and
poor righting reex
No gag reex
No gag reex
Oculocardiac/vago-vagal
reexapply pressure
to both eyes for several
minutes and check for
decreased heart rate
Inability to swallow,
regurgitation, voice
change, increased
heart rate and no crop
motility
TABLE 2. Continued
Nerve
XIa Accessory
XIIa Hypoglossal
Function
Parasympatheticglands,
heart and viscera
Motorsupercial neck
muscles
Motortongue, trachea
and syrinx
Clinical Test
Sign of Dysfunction
Inability to open and
close the glottis
Poor neck movement
Tongue grab
Tongue deviation
Modied with permission from Clippinger TL, Bennett RA, Platt SR. The avian neurological examination and ancillary
neurodiagnostic techniques. J Av Med Surg 1996;10(4):221-47.
a
Anastamoses present involving cranial nerves IX-XII.
TABLE 3. Reptile cranial nerves and their function and clinical tests to determine normal function and clinical
signs of dysfunction
Nerve
Function
Clinical Test
Sign of Dysfunction
Sensoryolfaction
II Optic
Sensoryvision
Menace reex
III Oculomotor
Motorpulls eye in or
x gaze;
Parasympathetic
controls iris and
ciliary body
Eyeball position
Menace reex
V Trigeminal
Ophthalmic branch
and maxillary branch
Mandibular branch
Motordraws gaze
anteriorly and
dorsally
Eyeball position
Sensoryfrom skin
around eye and
mouth. Sensory pits
of pit vipers and
boids.
Motorjaw adductor
muscles, muscles of
skin around teethbearing bones in
snakes and
intermandibularis (in
oor of mouth)
Lack of sensation
VI Abducens
Motordraws gaze
posteriorly
Eyeball position
VII Facial
Assess sensation
Palpebral reex
Voluntary opening of
mouth
VIII Auditory/Acoustic
Sensoryhearing
Response to sound
Sensorybalance and
coordination
Oculocephalic reex
Righting reex
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TABLE 3. Continued
Nerve
IX Glossopharyngeal
Function
Sensorytaste and
sensation in the
pharynx
Motorcontrols tongue
muscles
Clinical Test
Sign of Dysfunction
Gag reex
No gag reex
Dysphagia
X Vagus
XI Spinal accessory
Motortrapezius and
sternomastoid
muscles
XII Hypoglossal
Motorhyoid muscles
and tongue
Gag reex
No gag reex
Oculocardiac/vago-vagal
reexapply pressure
to both eyes for
several minutes and
check for decreased
heart rate
Inability to swallow,
regurgitation and ileus
Inability to open and close
the glottis
Tongue deviation
Adapted with permission from Wyneken J. Reptilian neurology: anatomy and function. Vet Clin North Am Exot Anim
Pract 2007;10:837-853.
FIGURE 1. Before hands-on physical examination, the patient should be examined from a distance. (A) Mute swan
(Cygnus olor) demonstrating neck weakness. (B) Harris hawk (Parabuteo unicinctus) presented with seizures because of
hypoglycaemia. (C) A juvenile emu with hindlimb paresis resulting from zinc toxicity after ingesting several zinc
screws and nails. (D) An aged Toulouse goose (Anser anser domesticus) with multiorgan failure demonstrating
torticollis. (E) Wild European kestrel (Falco tinnunculus) found unable to y presented with knuckling of the right foot
and absent withdrawal reex; note also the soiling of the tail feathers resulting from an inability to perch and preen
appropriately. (F and G) An aged blue-and-gold macaw (Ara ararauna) with pulmonary carcinoma demonstrating
Horner syndrome in the right eye (ptosis of the upper eyelid and miotic pupil); compare with the left eye of the
same bird.
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FIGURE 5. Hybrid falcon (Falco cherrug Falco rusticolus) perched on the gloved hand; the hand is rotated into
different positions to alter the birds centre of gravity,
forcing the bird to make compensatory movements to
retain balance.
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FIGURE 12. Wing of a domestic chicken being extended and then released to assess proprioception; the test is
repeated, and the wing tip is pinched to evaluate the withdrawal reex making note of any conscious perception
of pain.
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FIGURE 16. Proprioception being assessed in a domestic chicken by knuckling the toes of one foot over and
assessing speed and coordination with which the foot is
returned to normal standing position.
FIGURE 17. Before hands-on physical examination, the reptile patient should be examined from a distance. (A)
Dwarf reticulated python (Python reticulatus) with uraemic encephalopathy presented with seizures and incoordination. (B) Bosc monitor (Varanus exanthematicus) with severe nutritional secondary hyperparathyroidism (NSHP)
presenting with muscle fasciculation; note the abnormal posture, maloccluded jaw and deformity of the spine. (C)
Leopard gecko (Eublepharis macularius) presented with dysecdysis; this patient was suffering from NSHP. (D) Female
bearded dragon (Pogona vitticeps) demonstrating a head tilt and circling to the left. (E and F) Veiled chameleon
(Chamaeleo calyptratus) with a sunken left eye. (G) Corn snake (Pantherophis guttatus) with strabismus during recovery
from general anaesthesia.
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FIGURE 18. Panther chameleon (Furcifer pardalis) being encouraged to reach out and walk from one hand to
another.
FIGURE 19. Menace reex being performed on a Russian tortoise (Agrionemys horseeldii).
FIGURE 20. A food item (arrow) being offered to a panther FIGURE 21. Pupillary light reex testing in a Russian
tortoise.
chameleon in an attempt to assess vision.
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FIGURE 22. (A) Tail grip being assessed in a panther chameleon; (B) strength of coiled grip and demeanour being
examined in a king snake (Lampropeltis getula); note also the tongue icking, which suggests a degree of alertness.
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USEFUL TIPS
Some reptile species have the potential to cause
signicant injury to the examiner, especially during
examination of the head (e.g., monitors, iguanas,
large boids and venomous species) whereas some
species (e.g., iguanas) may attempt to whip the
FIGURE 27. (A) Cloacal tone and pinch reex being assessed in a Russian tortoise. (B) Prolapsed hemipenes in a king snake with
neoplasia of the spine.
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