Practical Tips to Perform Neurological Examination in Cats, CSF Taps and Myelography
World Small Animal Veterinary Association World Congress Proceedings, 2015
D. Lu, BVetMed, MVM, DECVN, CVA
Peace Avenue Veterinary Clinic, Mongkok, Hong Kong

Practical Tips To Perform Neurological Examination In Cats

Practice makes "purrrfect" - start practicing on your own cats, or incorporate into your physical examination on a nice cat patient.

Tip 1. Plan Consultation in Advance - Neurological Examination Starts with Observation

Cats are masters in hiding clinical signs. Plan the consultation in advance, allowing time for the owner to make video recording of the cat's abnormalities displayed at home, especially if it is fractious or timid and behaves differently in the clinic. Let the cat roams the consultation room (quiet and secured room - nobody opens the door accidentally). Observe and assess mental status, head/body posture and gait (any head tilt, head turn, circling, ataxia, weakness?).

Tip 2. Be Patient & Gentle, No Stress, Relax

Hands-on examination requires patience and tenderness as cats are less tolerant to repeated tests. Don't force yourself and the cat to complete a thorough neuro-examination.

Tip 3. Assess Postural Reactions

Minimal tests to evaluate a cat's proprioception and strength are:

 Paw positioning (knuckling test): Place the dorsal surface of the paw on the table - normal cat immediately replace it to the normal position. However, most cats are sensitive to their paws being touched and retract excessively. Perform tactile/visual placing instead.

 Paw positioning (reflex stepping): Place the foot on a sheet of cardboard/mouse-pad and pull sideways slowly. Normal cat reposition the paw when the leg is out 1–2 inches.

 Tactile placing: Hold the cat with one hand under the body and another hand tilt the head up (much easier than to cover the cat's eyes), then approach the table slowly. Normal cat places its foot on the surface immediately when the carpus touches the edge.

 Visual placing: Similar to tactile placing but allow the cat to see the table. Normal cats reach for the surface before the carpus touches the table.

 Wheel-barrowing: Support the cat's abdomen to shift centre of gravity onto the forequarters. Gently push cat forward to walk. A weak cat usually show low head carriage, roll forward (somersault), or collapse. Beware of some normal cat rolls over to avoid the test.

 Extensor postural thrust: Support the cat by the thorax caudal to the forelimbs and lower the hindquarters onto the floor. When the paws touch the surface, they should move in a coordinated walking-backward movement back to the weight-bearing position.

 Hopping individual leg: Pick up 3 legs and shift all weight onto the remaining leg. Normal cat extends the leg fully. Shift the cat's weight laterally (not medially!) and assess initiation, movement and strength.

Tip 4. Assess Muscle Tone, Spinal Reflexes

Flexing and extending the legs passively. Reflexes can be performed with the cat in lateral recumbency, or in standing position. Patellar and withdrawal reflexes are reliable.

 Patellar reflex: The stifle should be in a relaxed, flexed position. Normal response is a single, brisk extension of the stifle. If the recumbent cat is nervous and tense, test the lower leg closer to the ground.

 Withdrawal reflex: The limb should be fully extended. Apply a mildly painful stimulus (Pinch with fingers or hemostat) to the foot. Normal response is flexion of the entire limb.

Other reflexes are less reliable in cats and can be skipped.

Tip 5. Deep Pain Perception (DPP) Assessment: Comparison is the Key

Always evaluate DPP in every digit of each limb in plegic cats. Use the same device for consistency (e.g., hemostat). Some cats won't show the typical response (e.g., hissing/turning round/tachypnoea) despite intact DPP. Compare the plegic limb's DPP with the normal limb. Assume absent DPP if you cannot get a positive response consistently. Assess DPP of the tail and perineal region.

Tip 6. Avoid Over-Interpreting Spinal Pain

Leave spinal palpation to the last. Be tender and apply minimal stimulus that elicit a response. Some normal cats resent thoracolumbar palpation and show excessive rippling of cutaneous trunci muscle.

Tip 7. Do Not Miss Out the Pulses, the Joints and a General Physical Examination

Feline arterial thromboembolism and polyarthritis mimic spinal cord disease. Evaluate pulse quality, colour of nail beds and paws, temperature of the paretic limb, any muscle firmness or pain, and presence of joint effusion.

Practical Tips to Perform Cervical Cerebrospinal Fluid (CSF) Tap

1.  Correct positioning is vital. Flex the head 90 degrees, with the nose horizontal to the table-top. Ensure the endotracheal tube doesn't kink (use reinforced or armoured ET tubes).

2.  Identify the landmarks: Tip of the wing of the atlas and the occipital protuberance. Draw an imaginative vertical line between the tips of the wings of the atlas and a horizontal line from occipital protuberance to this vertical line. The site of needle insertion is the point half-way on this horizontal line.

3.  Insert the spinal needle through the skin, remove the stylet and advance the needle very slowly and horizontally until CSF appears in the hub.

4.  If you hit bone you are probably too caudal, re-direct the needle. In brachycephalic breeds the cerebellomedullary cistern is located more rostrally compared to non-brachycephalic breeds.

Practical Tips to Perform Lumbar Myelography

Use non-ionic, water-soluble (e.g., Iohexol), concentrations 240–300 mg iodine/ml. Dose: 0.25–0.5 ml/kg body weight.

Prepare contrast: warm up the bottle in a bowl of lukewarm water (less viscous contrast mixed better with CSF).

Use spinal needle with stylet: 22-gauge 1.5 inch is suitable in most cats.

Prepare patient (for a right-handed person, patient in right lateral recumbency): clip and aseptically prepare the lumbar cistern.

Locate L5/6 lumbar cistern: use your index finger to feel the spinous process of L6 - this is slightly rostral to the line drawn perpendicularly from the cranial border of left iliac crest felt by your middle finger. Flexing the hindlimbs forward (by your assistant) open up the lumbar cistern more. L6/7 cistern can be used in cats.

Insert the needle on top of L6 dorsal spinous process, direct it all the way towards the lamina. Once hit bone, "walk the needle" rostrally and slightly ventrally until pierce through the ligamentum flavum, onto the floor of vertebral canal. There is often (but not always) a "twitch" of the tail and pelvic limbs as the needle touches or penetrates the neural tissues. Remove the stylet and observe for any CSF flow. If there is no CSF flow, retract the needle slowly until CSF appears at the hub. Collect CSF whenever possible.

If there is no CSF, perform a test dose injection of 0.2–0.4 ml contrast. Remember to fill the hub with contrast before injection, to prevent iatrogenic introduction of air bubbles into the subarachnoid space.

Slowly inject the contrast, stop if there is increased pressure or if you are uncertain about the position of the needle tip. Take an x-ray to visualize the contrast. Once you finish the injection, gently and slowly remove the spinal needle. Don't wiggle the needle. I normally apply pressure using my finger on the injection site for a few seconds to reduce contrast backflow.

Tilt the animal's hindquarters up to aid the flow of contrast media rostrally (contrast flow by gravity), or elevate the head/neck and hindquarters with the thoracolumbar area at the lowest point to "pool" the contrast media to the area of interest. Take radiographs: lateral, ventrodorsal and oblique views.

Myelography is an invasive procedure and is associated with certain risks and complications.

Category of problem

How to prevent/solve problem

Disease-related

  

Excessive spinal cord swelling causing dispersing of all contrast media and inability to demonstrate the site or the side of lesion.

Use contrast media with higher iodine concentration to improve contrast (e.g., 300 mg instead of 240 mg iodine/ml).Taking radiograph as soon as contrast is being injected. Take oblique views in addition to lateral and ventrodorsal views. Consider MRI/CT-myelography if available.

Contrast/technique related

  

Seizure post-myelography

Avoid cervical myelography. Elevate the head and neck to prevent contrast flowing rostrally. Prepare intravenous diazepam.

Epidurogram - contrast media within the epidural space. Direct injection of contrast media into spinal cord parenchyma cause permanent damage and myelomalacia.

Slow injection (about 20–30 seconds for average size adult cat). Use test injection of 0.2–0.4 ml contrast. Fluoroscopy guidance.

Central canalogram - contrast injected into a normal-sized central canal cause acute hydromyelia, contrast enter the brainstem cause apnoea and death.

Avoid lumbar puncture site cranial to L4–5. Use test injection. Fluoroscopic guidance. Stop procedure if any unusual response occurs during injection (e.g., lordosis/scoliosis, tachypnoeic or apnoea), take radiograph to visualize location of contrast media.

    

References

1.  Sharp NJH, Wheeler SJ. Patient examination, diagnostic aids. In: Sharp NJH, Wheeler SJ, eds. Small Animal Spinal Disorders Diagnosis and Surgery. Edinburg, NY: Elsevier Mosby; 2005:19–34, 41–72.

2.  Lorenz MD, Coates JR, Kent M. Part I: Fundamentals. In: Handbook of Veterinary Neurology. 5th ed. St. Louis, MO: Elsevier Saunders; 2011:1–92.

3.  Scrivani PV. Myelographic artifacts. Vet Clin North Am Small Anim Pract. 2000;30:303–314.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Diane Lu, BVetMed, MVM, DECVN, CVA
Peace Avenue Veterinary Clinic
Mongkok, Hong Kong


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