Neurological Examination and Diagnostic Testing in Birds and Reptiles

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Neurological Examination and Diagnostic Testing in Birds and Reptiles Craig Hunt MRCVS

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S1557-5063(14)00213-4 http://dx.doi.org/10.1053/j.jepm.2014.12.005 JEPM564

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Journal of Exotic Pet Medicine

Cite this article as: Craig Hunt BVetMed, CertSAM, DZooMed, MRCVS, Neurological Examination and Diagnostic Testing in Birds and Reptiles, Journal of Exotic Pet Medicine, http://dx.doi.org/10.1053/j.jepm.2014.12.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

CLINICAL TECHNIQUE

Neurological Examination and Diagnostic Testing in Birds and Reptiles Craig Hunt, BVetMed, CertSAM, DZooMed, MRCVS

From the Chine House Veterinary Hospital, Sileby Hall, Sileby, Loughborough, Leicestershire, England, UK. Address correspondence to: Craig Hunt, BVetMed, CertSAM, DZooMed, MRCVS, Chine House Veterinary Hospital, Sileby Hall, Cossington Road, Sileby, Loughborough, Leicestershire, LE12 7RS, UK. E-mail: [email protected]. Telephone: 01509 812 446

Abstract Neurological dysfunction is a frequent 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 difficult cases, and to provide the owner with an accurate prognosis.

Key words: avian; examination; neurological; reflex; reptile

A 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 reflexes which are influenced 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 modifications may be required when performing a neurological examination on a bird or reptile patient due to differences in anatomy and temperament. Neurologic disease signs in birds and reptiles are often non-specific, 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 problems typically require extensive treatment prior to a full neurological assessment. Neurological disease in both birds and reptiles is often secondary to inadequate husbandry (e.g. temperature) and nutrition (birds and reptiles), but may be caused by toxins (e.g. heavy metals, organophosphates, pyrethroids, drugs, plants), infection (e.g. viral, parasitic, bacteria, fungus), neoplasia, congenital abnormalities, and cardiovascular, hepatic, and renal disorders. Metabolic diseases (e.g. hypocalcaemia) and musculoskeletal disorders (metabolic bone disease (MBD)) often present with similar clinical signs and may be difficult to distinguish from primary neurological disease without further investigation; hypothermia may also mimic neurological disease in reptiles. The evaluation of neurological disorders in reptiles and birds follows a similar pattern to that used for other species and begins by obtaining a thorough history and performing a detailed external physical examination. Further assessment of the patient will often include one or all of the following diagnostic modalities:

haematology

and

serum

biochemistry,

radiography,

ultrasonagraphy,

and

endoscopy. Additional diagnostic tests such as heavy metal analysis, serology/PCR for infectious diseases, and cerebral spinal fluid (CSF) analysis may be required in select bird or reptile neurologic cases. Increasingly computed tomography (CT) and magnetic resonance imaging (MRI) are becoming more accessible and may give detailed images of the central nervous system though the small size of many patients can be a limiting factor in the use of these advanced imaging modalities. Electromyography (EMG) and nerve conduction studies may be useful in selected cases but these tests are rarely available in the typical veterinary hosptial.

HISTORY All but the most compromised of avian and reptile patients will have normal behaviour under mild to moderate conditions of stress (e.g. veterinary visit). Observation of patients from afar in a quietened room, preferably after a period of acclimatisation, allows the patient to relax and display abnormal clinical signs, if present or behaviour which may otherwise go unnoticed. Whilst the patient is acclimatising, a thorough history may be obtained from the owner, giving the clinician time to evaluate the animal from a distance. This “hands-off” evaluation will allow the veterinarian to ascertain the patient’s ability to cope with restraint and physical examination and/or whether steps should be taken to medically stabilise the patient prior to handling. Important aspects of the history pertaining to the neurological patient include nutritional offering (including any supplements), what it is eating from what it is being fed and the patient’s ability to recognise and obtain food in an appropriate manner for that particular species, access to toxins, recent administration of medication, provision of appropriate ultraviolet light (many reptiles and some birds) and access to suitable thermal gradients (reptiles).

CLINICAL EXAMINATION

Much of the neurological examination may be incorporated into a well-structured physical examination. Following the physical examination the clinician’s goal is to localise the disease process to one or more areas of the nervous system. As stated previously, the natural behaviour of many avian and reptile patients routinely complicates the veterinarians’ ability to accomplish the task of localising the lesion associated with the neurological disease process The aim of the neurological exam is to localise any lesion to the brain (Table 2 and 3) or one of four major spinal cord divisions. The spinal cord divisions described in birds and reptiles are the cervical, brachial, thoracic, and lumbosacral plexus; snakes and presumably limbless lizards have reduced or absent brachial and sacral plexuses. Accurate localisation of pathology allows the clinician to determine which diagnostic test will confirm a disease diagnosis. Once a definitive disease diagnosis has been made, the veterinarian can form a prognosis and institute a treatment plan thus avoiding the unnecessary use of sometimes expensive and invasive tests.

HOW TO PERFORM A NEUROLOGICAL EXAMINATION: Equipment required to perform a proper neurologic examination on reptile and avian patients is provided in Table 1. Cranial nerve function tests for birds and reptiles and signs of neurologic dysfunction are in Tables 2 and 3 respectively.

Step-by-Step Guide for Birds:

(1.)

Observe the patient from a distance - assess posture and symmetry of head, facial features and body, demeanour, level of alertness and responsiveness to surroundings (Fig. 1)

(2.)

Make a loud noise such as clapping hands, dropping keys onto floor whilst the bird is otherwise occupied to assess hearing.

(3.)

Approach patient calmly and evaluate response to determine visual acuity and alertness. Note: birds with unilateral blindness often turn the blind side away from the examiner, therefore the blind eye is not easily observed.

(4.)

If tame, encourage the bird to step up onto and off a perch or hand (glove for raptors) noting coordination and strength of legs and grip (Fig. 2).

(5.)

Perform menace reflex by obscuring the vision in one eye with one hand whilst making a threatening gesture close to the opposite eye with the other hand, taking care not to cause any air movement which may be detected by the bird (Fig. 3).

(6.)

Drop and/or throw a ball of cotton wool in the patient’s normal field of vision and assess response. Assessing the response to being shown a favourite food item may also be performed and is especially useful in raptors and corvids.

(7.)

Assess the pupillary light reflex by shining a bright light into each eye and assess pupil response (Fig. 4). Note: there is no consensual response in birds.

(8.)

Whilst on hand/glove rotate hand in all directions to assess balance and strength of grip (Fig. 5).

(9.)

Lower hand quickly to stimulate a fall; the normal bird should extend wings +/flap to maintain balance. Observe for symmetry and speed with which the wings are returned to a normal resting position.

(10.) Palpate legs for symmetry, muscle mass and tone.

(11.) Pinch the toes of each foot in turn and asses the withdrawal response and determine whether there is any conscious perception of pain (Fig. 6); Caution

must be observed by the examiner! Raptors may strike out with their feet; parrots may attempt to bite.

(12.) At this point some patients may be restrained in a towel to allow access to the head whilst limiting wing and leg movement, which allows more control over the patient (Fig. 7).

(13.) Assess the palpebral reflex by lightly touching the medial canthus with a finger or cotton tipped applicator (Fig. 8).

(14.) Pinch the skin over the face and cere to assess facial sensation using finger or mosquito forceps (Fig. 9).

(15.) Open the beak to assess jaw tone, oral secretions, and observe the glottis and tongue for symmetry and normal movement (Fig. 10).

(16.) In non-psittacine birds, place the index finger of the hand restraining the head in the commisure of the beak to maintain the beak in an open position whilst manipulating the tongue and glottis with a cotton-tip applicator or a finger on the free hand to assess the gag reflex and tongue-grab reflex (Fig. 11). In psittacine birds the oral cavity is best opened and examined with the aid of a suitable speculum to avoid injury to the examiner.

(17.) Assess the oculocephalic reflex by moving the head from side to side whilst maintaining the head in a horizontal plane. In healthy birds nystagmus should be observed with the fast phase in the direction of the head movement.

(18.) Palpate the neck for muscle mass and tone and palpate the crop.

(19.) Extend each wing individually and pinch the wing tip to evaluate a withdrawal response and pain perception; then release the wing observing how quickly the bird retracts the wing into the normal resting position (Fig. 12).

(20.) Assess the muscle tone of the vent and then pinch or prick the vent with a needle; in the normal bird the vent sphincter should constrict (Fig. 13).

(21.) Whilst restraining the bird from above around the shoulders with the wings held against the body but with the legs unrestricted, bring the feet towards the examining table or a perch to evaluate the placing reflex (Fig. 14); raptors may be hooded to increase test sensitivity.

(22.) With the bird still restrained as described above and with one leg held up against the body wall, perform the hopping test on the standing leg by manoeuvring the patient’s body to change the centre of gravity laterally, medially, forward, and backward while measuring the compensatory movements of the leg (Fig. 15).

(23.) With the bird standing but with the body being supported, knuckle the toes of one foot over and evaluate how long it takes for the bird to return the foot to a normal position (Fig. 16); alternatively place a card under the foot and slide it laterally and evaluate the speed with which the bird returns the foot to a normal position.

(24.) Finally, pinch the skin or gently pull at the feathers along either side of the dorsal midline working methodically cranial to caudal or vice versa to assess cutaneous pain sensation. Note: birds lack a panniculus reflex.

Step-by-Step Guide for Reptiles:

(1.)

Observe the patient from a distance - assess posture and symmetry of head, facial features and body, demeanour, level of alertness, and responsiveness to surroundings. In snakes and monitor lizards note presence or absence of tongue flicking (Fig. 17).

(2.)

Make loud noise such as clapping hands, dropping keys onto floor whilst the patient is otherwise occupied to assess hearing. Note: many normal reptiles may not demonstrate a visible response.

(3.)

Approach patient calmly and observe response to assess vision and alertness. Note: many reptiles, especially lizards with unilateral blindness often turn the blind side away from the examiner.

(4.)

If tame, encourage the patient to climb up onto a perch/branch (chameleons/snakes) or hand (smaller lizards) noting coordination, muscle tone, and strength of grip (Fig. 18).

(5.)

Perform menace reflex by obscuring the vision in one eye with one hand whilst making a threatening gesture close to the opposite eye with the other hand taking care not to cause any air movement which may be detected by the reptile (Fig. 19)

(6.)

Drop and/or throw a ball of cotton wool in the patient’s normal field of vision and assess response. Judging an animal’s response to being offered a favourite food item (e.g. live insects) may is especially useful in insectivores (e.g. chameleons) (Fig. 20). Note: it may be difficult to completely differentiate an olfactory response from a visual one in some species.

(7.)

Assess the pupillary light reflex by shining a bright light into each eye and assess pupil response (Fig. 21). Note: the consensual response may be difficult to appreciate in reptiles.

(8.)

Whilst on hand/perch rotate hand in all directions to assess balance and grip. Snakes should be allowed to move from hand to hand and determine strength of coiled grip and strength in extension as the snake traverses the gap (Fig. 22).

(9.)

Palpate body and limbs (where present) for symmetry, muscle mass, and tone.

(10.) Extend each limb individually and pinch the toes to measure the withdrawal response and pain perception (Fig. 23); then release the limb whilst in

extension observing how quickly the limb is retracted into the normal resting position (caution must be observed by the examiner since some species may attempt to bite or tail whip).

(11.) Depending on the demeanour of the patient and to gain more control over the patient, either restrain in-hand or wrap the patient in a towel to allow access to the head whilst limiting leg and tail movement. Depending on the size and species, snakes may be allowed to coil around the examiner’s arm whilst being held behind the head with the examiner’s hand, or the body is supported by one or more assistants whilst the examiner holds the head.

(12.) Assess the palpebral reflex by lightly touching the medial canthus with a finger or cotton tipped applicator (Fig. 24). Note: it is not possible to assess the palpebral reflex in species without eyelids such as snakes and many gecko species

(13.) Pinch the skin over the face and head to assess facial sensation using finger or mosquito forceps or by pricking with a needle.

(14.) Open the oral cavity to assess jaw tone and observe the glottis opening and tongue for symmetry and normal movement and assess oral secretions (Fig. 25).

(15.) For smaller terrestrial tortoises, place the index finger in the commisure of the beak to maintain the mouth open and manipulate the tongue and glottis with a cotton-tipped applicator to assess the gag reflex and tongue-grab reflex (Fig. 26). A speculum may be required for larger species and/or those with sharp teeth and/or a powerful bite.

(16.) Assess the oculocephalic reflex by moving the head from side to side whilst maintaining the head in a horizontal plane. In healthy reptiles nystagmus should be observed with the fast phase in the direction of the head movement.

(18.) Palpate along the neck and spine for muscle mass and tone.

(19.) Assess the muscle tone of the vent and then pinch or prick the vent with a needle (Fig. 27); in the normal reptile the vent sphincter should constrict and the tail will often move to the side.

(20.) Roll the patient on both its left and right sides to assess the righting reflex (Fig. 28).

(21.) If the patient is a species with limbs, restraint should be achieved without restricting limb movement; bring each foot in turn towards the examination table or a perch (chameleons) to assess the placing reflex (Fig.29).

(22.) With the patient in a normal standing posture, hold the limbs on one side against the body wall and push the patient in a lateral direction (away from the side with the limbs restrained), repeat for the other side and evaluate the compensatory movements of the limbs (Fig.30).

(23.) Restrain the patient with only one foot standing on the examination table, perform the hopping test on the standing leg by manoeuvring the patient’s body to change the centre of gravity laterally, medially, forward, and backward and calculate the compensatory movements of the limb (Fig. 31).

(24.) With the patient standing but with the body supported knuckle the toes of one foot over and evaluate how long it takes for the patient to return the foot to a normal position (Fig. 32); alternatively place a card under the foot and slide it laterally and evaluate the speed with which the patient returns the foot to a normal position.

(25.) Finally pinch the skin along either side of the dorsal midline working methodically cranial to caudal or vice versa to assess cutaneous pain sensation. Note: reptiles lack a panniculus reflex.

USEFUL TIPS Some reptile species have the potential to cause significant injury to the examiner, especially during examination of the head (e.g. monitors, iguanas, large boids, venomous species) while some species (e.g. iguanas) may attempt to whip the examiner with their tail. Raptors may strike with their talons and psittacines and some raptors (especially vultures and eagles) can deliver a substantial bite. Ratites can deliver a powerful kick which can cause serious injury. The ciliary muscle is under voluntary control in birds and reptiles giving these species the ability to override the pupillary light reflex (PLR) particularly when the animal is stressed.

The pupillary light reflex is best performed early in the

examination, preferably with the patient unrestrained, to minimise stress effect on the test results.

SUMMARY Birds and reptiles present unique challenges to the veterinarian attempting to investigate and diagnose neurological conditions in these species. Performing an adequate neurologic examination on avian and reptile patients is perceived by many veterinarians as a formidable challenge due to the wide variations in anatomy, physiology, and demeanour but success can be achieved by adapting recognised examination techniques utilized for dogs and cats.

References

1. Bennet RA: Neurology, in: Ritchie BW, Harrison GJ, Harrison LR (eds) Avian Medicine: Principles and Application. Lake Worth, FL, Wingers Publishing pp 728-747, 1994

2. Dubbeldam JL: Motor control system, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 83-100, 2000

3. Gu ntu rku n O: Sensory physiology: Vision, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 1-20, 2000

4. King AS, McClelland J: Birds: Their Structure and Function (ed2). Bath, United Kingdom: Bailliere Tindall pp 237-315, 1984

5. Kuenzel W: The autonomic nervous system of avian species, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 101-122, 2000

6. Mason JR, Clark L: The chemical senses in birds, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 39-56, 2000

7. Molenaar GJ: Anatomy and physiology of infrared sensitivity of snakes, in Gans C, Ulinski P (eds). Biology of the Reptilian. Vol. 17 (neurology C). Chicago, IL, University of Chicago Press pp 367-453, 1992

8. Necker R: Functional organization of the spinal cord, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 71-82, 2000

9. Necker R: The avian ear and hearing, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp. 21-38, 2000

10. Necker R: The somatosensory system, in Whittow GC (ed): Sturkie’s Avian Physiology (ed5). San Diego, CA, Academic Press pp 57-70, 2000

11. Orosz SE, Bradshaw GA: Avian neuroanatomy revisited: from clinical principles to avian cognition. Vet Clin North Am Exot Anim Pract 10:775-802, 2007

12. ten Donkelaar HJ, Bangma GC: The cerebellum, in Gans C, Ulinski P (eds): Biology of the Reptilian. Vol. 17 (neurology C). Chicago, IL, University of Chicago Press pp 496-586, 1992

13. Ulinski PS, Dacey DM, Sereno MI: Optic tectum, in Gans C, Ulinski P (eds): Biology of the Reptilian. Vol. 17 (neurology C). Chicago,IL, University of Chicago Press pp 241-366, 1992

14. Wyneken J: Reptilian neurology: anatomy and function. Vet Clin North Am Exot Anim Pract 10:837-853, 2007;

15. Jaggy A, Spiess B: Neurological examination of small animals, in Jaggy A (ed): Small Animal Neurology. Hannover, Germany, Schlutersche pp 1-37, 2010

FIGURE LEGENDS (Figure 1.)

Prior to 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 as a result 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 multi-organ failure demonstrating torticollis (e) Wild European kestrel (Falco tinnunculus) found unable to fly presented with knuckling of the right foot and absent withdrawal reflex, 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’s syndrome in the right eye (ptosis of the upper eyelid and miotic pupil), compare to the left eye of the same bird.

(Figure 2.)

Hybrid falcon (Falco cherrug X Falco rusticolus) stepping up onto a Tperch from the gloved hand

(Figure 3.)

Menace reflex being performed on a domestic chicken; note the head reaction.

(Figure 4.)

Pupillary light reflex being assessed on a domestic chicken; this test is best performed early in the examination to minimise conscious reaction of the pupil which often occur during excitement or stress in birds.

(Figure 5.)

Hybrid falcon (Falco cherrug X Falco rusticolus) perched on the gloved hand; the hand is rotated into different positions to alter the bird’s centre of gravity forcing the bird to make compensatory movements to retain balance.

(Figure 6.)

The withdrawal reflex performed on a hybrid falcon (Falco cherrug X Falco rusticolus) noting withdrawal response and any conscious perception.

(Figure 7.)

African grey parrot (Psittacus erithacus) being wrapped in a towel to allow control over the head; this procedure is not always necessary depending on the patient’ demeanour.

(Figure 8.)

Palpebral reflex being elicited in a domestic chicken by gently touching the medial canthus with a cotton tipped applicator.

(Figure 9.)

Facial sensation being assessed in a domestic chicken by gently pinching the comb, wattles, cere, and facial skin using fingers or forceps.

(Figure 10.) Jaw tone being assesses in a domestic chicken by gently opening the beak; the oral cavity and glottis are assessed for symmetry and the presence of any lesions.

(Figure 11.) In non-psittacine birds, the index finger of the hand restraining the head is placed in the commisure of the beak to maintain the beak in an open position whilst manipulating the tongue and glottis with a cotton-tip

applicator or a finger on the free hand to assess the gag reflex and tongue-grab reflex. In psittacine birds the oral cavity is best opened and examined with the aid of a suitable speculum to avoid injury to the examiner.

(Figure 12.) Wing of a domestic chicken being extended and then released to assess propriception; the test is repeated and the wing tip pinched to evaluate the withdrawal reflex making note of any conscious perception of pain.

(Figure 13.) Cloacal muscle tone and pinch reflex being measured in a domestic chicken.

(Figure 14.) Placing reflex in a domestic chicken (raptors may be hooded to increase test sensitivity).

(Figure 15.) The hopping test is being performed on a domestic chicken.

(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.) Prior to hands-on physical examination the reptile patient should be examined from a distance (a) Dwarf reticulated python (Python reticulatus) with uremic 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

(Figure 18.) Panther chameleon (Furcifer pardalis) being encouraged to reach out and walk from one hand to another.

(Figure 19.) Menace reflex being performed on a Russian tortoise (Agrionemys horsefieldi)

(Figure 20.) A food item (arrow) being offered to a Panther chameleon in an attempt assess vision.

(Figure 21.) Pupillary light reflex testing in a Russian tortoise.

(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 flicking which suggests a degree of alertness.

(Figure 23.) The withdrawal reflex performed on a Panther chameleon noting withdrawal response and any conscious perception.

(Figure 24.) The palpebral reflex being assessed in Russian tortoise.

(Figure 25.) Detemination of a Russian tortoise’s jaw tone can be achieved by gently opening the mouth; the oral cavity and glottis opening are assessed for symmetry and the presence of any lesions.

(Figure 26.) Gag reflex and tongue-grab reflex being assessed in a Russian tortoise using the index finger as a specula.

(Figure 27.) (a) Cloacal tone and pinch reflex being assessed in Russian tortoise; (b) Hemipene prolapse in a king snake with neoplasia of the spine.

(Figure 28.) Righting reflex being assessed in red iguana (Iguana iguana); this patient failed to return to a normal standing position.

(Figure 29.) Placing reflex being assessed in a Russian tortoise.

(Figure 30.) Hemi-standing being assessed in a Russian tortoise.

(Figure 31.) Hopping test being performed on a Russian tortoise.

(Figure 32.) Proprioception being evaluated in a bearded dragon by knuckling the toes of one foot over and assessing speed and coordination with which the foot is returned to a normal standing position.

Table 1. Equipment list 1)

Pen torch

2)

Hypodermic needles

3)

Mosquito forceps

4)

Towel

5)

Gloves

6)

Perch

7)

Digital thermometer

8)

Mouth gags

9)

Cotton-tip applicators

Table 2 Avian cranial nerves, their function, clinical tests to determine normal function and clinical signs of dysfunction Nerve

Function

Clinical Test

Sign of dysfunction

I Olfactory

Sensory - olfaction

Response to odour

No response; beware that

such as alcohol;

aversion is not always due

Patient should avoid

to odour but to physical

noxious odour

irritation

Menace reflex

Absent blink and/or

II Optic

Sensory - vision

aversive movements of head and body in response to a threat. Inability to avoid objects placed in path III Oculomotor

IV Trochlear

Motor – extrinsic ocular muscles

Eyeball position and

Ventrolateral deviation

and upper eyelid muscle

movement

Drooped upper eyelid

Parasympathetic – intrinsic ocular

Menace reflex

Dilated pupil

muscle

Pupillary light reflex

Motor – extrinsic ocular muscle

Eyeball position and

Dorsolateral deviation

movement V Trigeminal: Ophthalmic branch

Maxillary branch

Sensory (upper lid, forehead skin, nasal cavity, upper beak)

Response to touch,

Lack of sensation

Sensory (both lids, hard palate,

Palpebral reflex

Unable to blink

nasal cavity, lateral upper beak)

Menace reflex

Motor (orbicularis, lower lid,

Unable to close jaw

chewing) Mandibular branch

Sensory (lower beak skin commisures)

VI Abducens

VII Facial

Motor – extrinsic ocular muscles,

Eyeball position and

Medial deviation

nictitans

movement

Nictitans immobility

Motor – facial expression

Facial asymmetry

Sensory – taste

Poor taste

Parasympathetic - most glands of

Decreased secretions

the head VIII

Sensory – hearing

Response to sound

No response to sound, head

Vestibulocochlear

Sensory – balance and

Oculocephalic reflex

tilt, nystagmus, abnormal

coordination

Righting reflex

posture, poor righting reflex

IXa

Sensory - taste and sensation in

Glossopharnygeal

the tongue and trachea

Gag reflex

Motor – pharynx, larynx, crop and

No gag reflex

Dysphagia, voice loss

syrinx a

X Vagus

XIa Accessory a

XII Hypoglossal a

Sensory – larynx, pharynx,

Gag reflex

No gag reflex

viscera

Oculocardiac/vago-

Inability to swallow,

Motor - larynx, pharynx,

vagal reflex - apply

regurgitation, voice change,

oesophagus, crop

pressure to both eyes

increased heart rate, no crop

Parasympathetic –glands, heart

for several minutes

motility

and viscera

and check for

Inability to open and close

decreased heart rate

the glottis

Motor – superficial neck muscles Motor – tongue, trachea, syrinx

Poor neck movement Tongue grab

Tongue deviation

Anastamoses present involving cranial nerves IX – XII

Modified from Clippinger TL, Bennett RA, Platt SR. The Avian Neurological Examination and Ancillary Neurodiagnostic Techniques. J Av Med Surg 1996;10(4):221-47; with permission

Table 3 Reptile cranial nerves, their function, clinical tests to determine normal function and clinical signs of dysfunction Nerve

Function

Clinical Test

Sign of dysfunction

I Olfactory

Sensory – Olfaction

Patient should avoid

No response; beware that

(including the

noxious odour such

aversion is not always due

vomeronasal nerve

as alcohol or show

to odour but to physical

branch)

ability to find food

irritation

when eyes are covered II Optic

Sensory - Vision

Menace reflex

Absent blink (in species with eyelids) and/or aversive movements of head and body in response to a threat. Inability to avoid objects placed in path

III Oculomotor

Motor - pulls eye in or fix gaze;

Eyeball position

Abnormal eyeball position,

Menace reflex

movement and pupil shape/size; Dilated pupil

Parasympathetic - controls iris

Pupillary light reflex

and ciliary body IV Trochlear

Motor - draws gaze anteriorly and

Eyeball position

dorsally

Abnormal eyeball position and movement

V Trigeminal Ophthalmic branch

Sensory - from skin around eye

Assess sensation

and

and mouth. Sensory pits of pit

around face, lower lid

Maxillary branch

vipers and boids.

and nasal area

Mandibular branch

Motor - jaw adductor muscles,

Lack of sensation

Unable to close jaw

muscles of skin around teeth-

Assess normal jaw

bearing bones in snakes, and

closure and buccal

intermandibularis (in floor of

pumping.

Absent buccal pumping

mouth) VI Abducens

Motor - draws gaze posteriorly

Eyeball position

Abnormal eyeball position and movement

VII Facial

Sensory - from skin and muscle

Assess sensation

Unable to move eyelids (in

around the ear, upper jaw and

Palpebral reflex

species with eyelids).

pharynx.

Unable to open mouth

Motor - superficial neck muscles

Voluntary opening of

and mandibular depressor

mouth

voluntarily

VIII

Sensory – hearing

Response to sound

No response to sound, head

Auditory/Acoustic

Sensory – balance and

Oculocephalic reflex

tilt, nystagmus, abnormal

coordination

Righting reflex

posture, poor righting reflex

IX

Sensory - taste and sensation in

Gag reflex

No gaga reflex

Glossopharnygeal

the pharynx

Examine tongue for

Absent or abnormal tongue

Motor - controls tongue muscles

active protrusion and

movements

retraction Observe

Dysphagia

ability to swallow X Vagus

Sensory and motor to the glottis,

Gag reflex

No gag reflex

heart and viscera

Oculocardiac/vago-

Inability to swallow,

vagal reflex - apply

regurgitation, ileus

pressure to both eyes

Increased heart rate

for several minutes

Inability to open and close

and check for

the glottis

decreased heart rate

XI Spinal

Motor - trapezius and

Assess muscle tone in

Poor muscle tone in neck

Accessory

sternomastoid muscles

dorsal neck and

and shoulders.

shoulders (difficult to

Poor neck movement

assess in snakes and chelonia) XII Hypoglossal

Motor - hyoid muscles and

Tongue grab

Tongue deviation

tongue Adapted from Wyneken J. Reptilian Neurology: Anatomy and Function. Vet Clin North Am Exot Anim Pract 2007; 10:837-853; with permission.