Myasthenia Gravis in a Persian Cat - A case report

 

        A five-year-old Persian cat presented with a complaint of acute onset paraplegia progressing to tetraplegia the following day. These signs started a day after a grooming session. The details of the  Neurological examination performed is described below.

Signalment -5-year-old neutered male, DSH CAT

Weight: 4.9 Kg 

Heart Rate: 120 bpm

Capillary Refill Time : <2sec

Mucous Membrane: PINK

Neurological Exam

Neurological History

The owner noticed her cat is not able to bear weight on any of its legs ever since a grooming session a day before. The cat is able to have food and pass urine and stools normally. A similar incident occurred exactly 12 months before which got better with intravenous Meropenem and 5 sittings of class-4 LASER. No signs of pain were noticed by the owner. Conscious control of urination and defecation was present

PHYSICAL EXAM

Comment: The cat was cooperative and well-tempered

The cat was quiet, active, responsive, well-hydrated and non-ambulatory

Head: no significant findings

Chest: clear lungs bilaterally

Abdomen: caudally loose on palpation, no abnormality detected 

Integument: no significant findings

Lymph node: within normal limits

Musculoskeletal: not able to bear weight completely on hind limbs. Forelimbs - partial weight bearing but soon slipped and came down on all 4 limbs.

Mentation: Normal

Behavior: Normal

Posture: wide-based stance briefly when supported

Gait: non-ambulatory

Postural Reactions

Both Forelimbs paw placement - sluggish/absent

Both Pelvic limbs paw placement - absent 

Hopping forelimbs - sluggish

Hopping hindlimbs - absent

Wheel borrowing - absent 

Cranial nerves: Normal

Pelvic Reflexes

Absent patellar reflex bilaterally

Cranial tibial reflex - did not check

Sciatica reflex - did not check

Perineal Reflexes 

Anal reflex - sluggish but present 

Withdrawal reflex: present in all 4 limbs 

Deep Pain Perception: present in all 4 limbs

Spinal Palpation: Normal 

Cutaneous Truncii Reflex: Twitching of the muscles absent at all following levels - L6 -T13, T13-T3, present cranial to T3

Video of the physical examination of the cat showing signs of muscular weakness resembling tetraplegia

Summary - This was an acute/ subacute progressive condition. No painful lesions were palpable on the spine and appendicular skeleton.  An intrathecal lesion in the cervical spinal cord or at a level cranial to T3-T4? 

DIFFERENTIAL DIAGNOSES

1. IVDP

2. CERVICAL SPONDYLOMYELOPATHY WITH SECONDARY DISC COMPRESSION

3. NEOPLASIA

4. DEGENERATIVE MYELOPATHY

5. MENINGOMYELITIS

6. NEUROMUSCULAR JUNCTION DISORDERS - MYASTHENIA GRAVIS

Conservative treatment was opted initially assuming meningomyelitis was the cause and when the cat failed to respond to the treatment, the owner was advised to get an MRI done. 

TREATMENT - 

DAY 1 - Anti-inflammatory dose of steroid - prednisolone + Neurokind + LASER

DAY 2 - Anti-inflammatory dose of steroid + 30mg/kg Meropenem bid + LASER

DAY 3 -Anti-inflammatory dose of steroid + 30mg/kg Meropenem bid + LASER

DAY 4 - Discontinuation of mediations by the owner

DAY 5 - LASER

DAY 6 - MRI performed under sedation. 

MRI revealed no significant neurological finding that could explain the clinical signs exhibited. 

    Following the interpretation of MRI findings, the only differential that had to be ruled out was Myasthenia gravis. 0.04 mg/kg of neostigmine was administered IM to diagnose suspected Myasthenia Grevis through 'response to treatment'. No significant improvement was seen. Ideally, a Tensilon test needed to be performed for this purpose but due to the lack of availability of edrophonium, Neostigmine was used. Although, the effects of neostigmine are not visible as rapidly as are with edrophonium, at least a delayed favorable response should be observed. The owner noticed signs of improvement the day after administration of neostigmine. Oral pyridostigmine was prescribed for an initial period of 1 month (1/4th tablet of Gravitor ^® 30mg once a day). 

        Not having got any updates from the owner over the phone, I assumed both the cat and the owner had accepted the inevitable.  It was a sight to behold when the owner got in the cat for a review after a couple of months and the kitty was jumping around just as it was doing before his illness! 

  

Video of the cat walking normally 2 months after the initiation of oral pyridostigmine.

        An Acetyl Choline Receptor Antibody titer would have been the confirmatory diagnostic test in this case. A value of >0.50mmol/L would indicate a positive result for Myasthenia Gravis. However, the test wasn't performed initially because 'response to treatment' was the economical option and since that succeeded, the owner didn't want to conform the same with another test later on. 

        Sometimes, the nature of diseases makes us look dumb and humbles us as veterinarians. All the expensive antibiotics and potent steroids used went down the drain. The harsh truth is we sometimes just shoot in the dark and hope to hit the target. Not having access to advanced diagnostics in-house, the lack of specialists in the field, the disinclination of the owners to spend on 'unwanted tests', and the impatience of clients to seek a second opinion from a 'famous vet' often hinders the course of action taken by the primary attending veterinarian. This case also reiterates the importance of advanced diagnostics, patience and perseverance the client and the vet require in dealing with neurological cases.