Gait – an introduction

37 Gait – an introduction

Weakness (paresis) or paralysis, ataxia, and lameness are the most commonly observed alterations in gait.

PARALYSIS AND PARESIS

Paralysis

is the absence of voluntary movement.

Paresis

is reduced voluntary movement.

Paresis may manifest as

• Difficulty rising from sitting

• Collapse, falling

• Unable or unwilling to exercise.

• Unable to jump into the car, go up stairs or climb onto furniture

• Unable to support self on one hind limb while urinating

• Unable to maintain a squatting position to urinate/defecate

• Slow moving or shuffling gait

• Dragging/scuffing/scraping/abrading the dorsum of the paw on the ground

• Dragging self using forelimbs alone

• Decreased limb extension: plantigrade stance, crouching gait

• Increased limb extension (stiff or stilted) with short steps followed by collapse

• Synchronous use of both hindlimbs (bunny hopping).

Some of these descriptions also apply to animals with orthopaedic disease causing lameness.

The affected limbs are discovered by observation and by provoking movement with postural reaction testing.

DEFINITIONS

The animal is described as

• Tetraplegic or quadriplegic: paralysed in all four limbs

• Non-ambulatory tetraparetic: weak in all four limbs. Able to move all limbs but unable to stand and walk unaided

• Ambulatory tetraparetic: weak in all four limbs but able to walk unaided

• Hemiplegic: paralysed in the forelimb and hindlimb of one side

• Hemiparetic: weak in the forelimb and hindlimb of one side

• Paraplegic: hindlimb paralysis

• Paraparetic: hindlimb weakness

• Monoplegic: weakness of one limb. Usually described by stating which limb is affected and how badly, e.g. paralysis of the right forelimb or weakness of the left hindlimb.

CLINICAL TIP

Do not forget that weakness or paralysis may also occur in other parts of the body causing dysphagia, regurgitation, dysphonia, absent blink, inspiratory dyspnoea, inability to prehend or altered neck posture. Always check the history and the cranial nerve function.

LOCALIZATION

A chain of synapsing neurons is called a pathway. A pathway in the CNS may be known as a tract, fasciculus, peduncle, or lemniscus. Small bundles of neurons in the PNS are called fascicles which combine to create nerves.

Descending tracts from the brain transmit the impulses which make the animal move. The impulses gain access to the muscles via nerves.

• Damage to the descending pathways causes paresis/paralysis

• Damage to the nerves causes paresis/paralysis

• Damage to the connection between nerves and muscles, the neuromuscular junction, causes paresis/paralysis

• Damage to muscle tends to cause paresis rather than paralysis.

CLINICAL TIP

Most damage to the cerebrum does not cause obvious paresis or paralysis. Such animals walk with a normal gait. Postural reactions can detect a subtle paresis.

Differentiating the cause of paralysis requires examination of the limb’s nerve function: muscle tone and reflexes. If the tone and the reflexes are intact, present, normal (2+) or increased (3+, 4+) on examination it means that those nerves, and the spinal cord segments of their origin, are functioning and are not responsible for the weakness or paralysis.

Fantastic! A functioning reflex arc means a whole chunk of the nervous system works! The cause of the weakness therefore lies in the descending tracts cranial to the weak or paralysed limb.

But…if the tone and reflexes are reduced (1+) or absent (0) on examination it means that those reflex arcs do not work and somewhere in that reflex pathway is to be found the lesion causing weak or paralysed limbs (Fig. 37.1) (see p 20, Table 2.3).

Figure 37.1 Motor deficits in spinal cord lesions.

Tags: Saunders Solutions in Veterinary Practice Small Animal Neurology

Sep 3, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

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