You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Ventroflexion of the neck is seen occasionally in cats and there are several known causes which need to be differentiated

Ventroflexion of the neck in cats is usually accompanied by generalised neuromuscular weakness so other locomotor signs may be present. Diagnosis is made on clinical signs and various laboratory tests, but sometimes trial and error testing with preparations (eg thiamine) is needed to determine the cause.

A cat with ventroflexion of the neck 

(Photograph reproduced with the kind permission of Hill's Pet Nutrition)

Ventroflexion of the neck  is typically found in the following conditions (which are listed alphabetically) :

• Ammonium chloride toxicity
  • Seen occasionally. 
  • When ammonium chloride is used as a urine acidifier in the management of urolithiasis the acidosis increases potassium loss through the kidneys - and the resulting hypokalaemia causes muscle weakness and neck ventroflexion
• Hereditary neck ventroflexion
  • Rare. 
  • An inherited defect has been described in Burmese cats (in the UK and Australia) which causes episodic stress-induced muscle weakness and neck ventroflexion. Cause not fully understood. May be transient hypokalaemia or thiamine deficiency may be involved. Affected cats should not be bred from.
  • Young Devon Rex cats (in the UK) have also been recognised with ventroflexion of the neck. It is reported to be due to congenital muscular dystrophy. 
• Hypernatraemia
  • Rare. 
  • This is seen in hypernatraemic cats which are hypodipsic. The signs are transient and thought to be due to low intracellular potassium. Creatine phosphokinase (CPK) is increased.
• Hyperthyroidism
  • Uncommon. 
  • A small percentage (<20%) of hyperthyroid cats will have muscle weakness and 1-3% will have ventroflexion of the neck. The cause may be due to thyrotoxicosis or secondary due to inappetance and thiamine deficiency.
• Hypocalcaemia
  • Rare
  • Hypocalcaemia sometimes causes neck ventroflexion. Other muscular signs include fasciculations, spasms, tetany and seizures. 
• Hypokalaemia
  • A common cause of neck ventroflexion and generalised muscle weakness
  • 30% of cats with chronic renal disease are hypokalaemic but only a few show neck ventroflexion. There is usually a high CPK as well as low serum potassium. Acidosis is an important factor in the development of hypokalaemia, and loop diuretics encourage potassium loss. Azotaemia is also present.
  • Potassium supplementation should be given as soon as the diagnosis is confirmed (as the gluconate or chloride) Dose - 5-10 mEq divided twice daily orally to cats with <3 mEq/l serum potassium.
  • Improvement seen over 1-3 day period.
  • Feed a ration containing at least 0.6% potassium
  • Treat underlying disease - use only potassium-sparing diuretics if necessary.
• Idiopathic polymyositis
  • Uncommon
  • Causes generalised muscle weakness, a stiff gait, muscle pain and ventroflexion of the neck.
  • Normal serum potassium, increased CPK, myofiber necrosis and lymphocytic infiltration is seen on histopathological examination of muscle biopsies.
  • Cause - unknown - maybe immune-mediated
• Myasthenia gravis
  • Uncommon
  • Both congenital and acquired myasthenia gravis occurs in cats
  • Neck ventroflexion is the only clinical sign in 50% of these cases
  • Other signs include : generalised weakness, abnormal gait, lagophthalmos. Occasional signs are muscle tremors, regurgitation of food and change in the voice.
  • Serum chemistry results are usually normal
  • Improvement in signs is obtained by the administration of an ultra-short acting acetylcholinesterase inhibitor (eg edrophonium chloride  (0.5-1.0 mg/kg) , or neostigmine (100 micrograms/kg) . Care is needed with this test  in case respiratory arrest is precipitated.
  • Anticholinesterase antibodies (AChR antibodies) will be present in cats with acquired myasthenia gravis, but not in cats with congenital myasthenia.
  • Muscle action potentials decrease in magnitude during repeated stimulation tests - but this is corrected by the administration of edrophonium. 
  • Long term treatment is provided by pyridostigmine bromide - a long acting acetylcholinesterase inhibitor - dose 2mg/kg by mouth every 8-12 hours.
• Organophosphate poisoning
  • Cats are particularly susceptible to develop organophosphate toxicity (eg to insecticides) and the effects can be subacute or chronic following multiple exposures. The result is acetylcholinesterase inhibition producing a myasthenia-type disorder with muscle weakness and ventroflexion of the neck. 
  • Other signs include dilated pupils, and muscle tremors.
  • If edrophonium is given to these cases their condition may worsen, and edrophonium does not eliminate the decreased action potential in repeatedly stimulated muscle.
  • Atropine will not block the nicotinic receptor overstimulation that causes the neck ventroflexion, but diphenhydramine does (4mg/kg by mouth every 8 hours). This drug must be used with caution in cats - side-effects include CNS excitation, sedation and anorexia.
• Polyneuropathy (idiopathic or secondary)
  • Rare
  • Secondary polyneuropathy associated with diabetes mellitus is the most often recorded - but this form of polyneuropathy causes poor posture and slow limb reflexes not ventroflexion of the neck.
  • Idiopathic polyneuropathy does lead to ventroflexion of the neck.
• Portosystemic encephalopathy
  • Uncommon sign seen with this disease.
  • Other signs include depression, stupor, pacing, circling, ataxia, blindness, collapse, head pressing, personality changes, seizures, hyperactivity, ventroflexion of the neck, muscle tremors, deafness and coma.
  • Diagnosis based on clinical signs, elevated liver enzymes on blood chemistry and high fasting blood ammonia and abnormal serum bile acid concentrations
• Thiamine deficiency
  • Uncommon
  • Thiamine (Vitamin B1) deficiency is uncommon as commercially prepared complete cat foods contain adequate concentrations, however many cases of ventroflexion of the neck in cats are thiamine-responsive. 
  • Thiamine is a co-enzyme needed for energy production and deficiency causes polyneuropathy and polymyopathy
  • Other signs include dilated pupils with a poor light reflex.
  • Thiamine is given at 25-50mg daily by intramuscular injection for 2-3 days.
  • Head carriage returns to normal in 1-2 days
  • Creatine kinase (CPK) concentrations may increase after thiamine treatment

 Last updated : October 2013