Paralysis of one limb, monoparesis

Monoparesis means weakness of one limb. If animal is weak just in one limb the gait pattern is frequently mistaken by the dog owners as lameness. On the other hand signs of paralysis and pain are frequently present simultaneously as diseases affecting one nerve or nerve root will frequently cause dysfunction of the nerve (paralysis) and pain. If just one limb is paralysed it is rarely the disease of the spinal cord, more frequently focal diseases of the nerve(s) or muscle(s) will cause the symptoms. The most frequent are the conditions affecting the nerve roots. Nerve root is the very beginning of the nerve which is leaving the spinal cord and getting outside the spinal canal through the foramen between the two vertebras. This foramen is the narrowest place anatomically and the most frequent place for the mechanical compression of the nerve to occur in dogs and cats. On the other hand it is also good, that the nerve roots and the intervertebral foraminas can be well visualised with the help of magnetic resonance imaging and the compression detected. In contrary, the visualisation of the peripheral nerves is not so easy but can be performed with the help of ultrasound or examined with the help of measuring the nerve conduction velocity.

The most important nerves in the front limb of the dog are the radial, ulnar, median, musculocutaneous and suprascapular nerves. From the mentioned nerves the most usually affected and inevitable nerve is the n.radialis. If radial nerve is damaged, the animal will show severe lameness-weakness in the affected limb. The other mentioned nerves of the front limb are less important as even severe lesions to the nerves will cause just mild gait abnormalities.

The important nerves in the hind limb are two: sciatic and the femoral nerve. Damage to any of them will severely affect the gait of the patient.

The most frequent causes for the nerve damage in veterinary neurology are traumas and the stenosis of the intervertebral foraminas or stenosis of the whole spinal canal in the lumbosacral area. Traumatic lesions are frequent in both dogs and cats. Car accidents sometimes cause trauma to the multiple nerves of the front limb or the whole plexus brachialis. Fractures of the tail or sacrum in cats sometimes are causing severe dysfunction of the both sciatic nerves. The best therapy to the peripheral nerve trauma is physiotherapy. The damaged nerves are rarely sutured in veterinary medicine. The good news with the traumas to the nerves is that the peripheral nerve regeneration is possible if the nerve is not completely transacted. The regrowth of the nerve is happening gradually approximately 1mm per day.

The most frequent causes of monoparesis in dogs are the foraminal intervertebral disk herniations and the degenerative lumbosacral stenosis. Foraminal intervertebral disk hernaitions are actually the disk herniations where the disk material has moved to the side of the spinal canal and is pressing the nerve root. This type of problems is more frequent in dogs in one of the front limbs. The diagnosis is made after the magnetic resonance imaging and the surgical removal of the disk material which is pressing the nerve is the best treatment. Degenerative lumbosacral stenosis is actually the disease of the last two lumbar vertebras and the sacrum. Lumbosacral junction is the area causing the most of the pains in the lower back in humans and in dogs. It is still not clearly understood why exactly this part of the spine is so frequently affected. Some researches believe it is because the intervertebral disk between the last lumbar vertebra and the sacrum is the biggest in the body therefore it is prone to degenerative changes. The others believe that the forces between the vertebras in this area are the strongest causing excessive motion-instability and secondary changes such as thickening of the ligaments, tearing of the intervertebral disk and others. It seems that the factors are multifactorial. The diagnosis in this condition is best done with the help of magnetic resonance imaging and the therapy plan is dependent on the location of stenosis but usually the surgical therapy is preferred.

• Referral/Question/Feedback
• Patient of the month
• Scientific publications
• Neurology for vets
• Important links