“Head-down syndrome” in a rabbit

Possible causes

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Kathleen Bourdelais Midnight (black rabbit) is happily living with 2 other rabbits. The days before the inability to hold its head high, Midnight was healthy, with an upright head, no appearance of the third eyelid.

Acute onset of “head-down syndrome”, also referred to floppy head syndrome or dropped head syndrome, has been observed in rabbits. The head is tilted forward and rabbits appear to be unable to lift it. The forward flexion is caused by weakness or contraction of the extensor muscles in the neck, which leads to the inability to hold the head upright and against the force of gravity. There is no tilting to the side. It may be accompanied by reluctance to move, decrease of appetite and pain.

Reminder: rabbits feel very insecure on smooth, slippery surfaces or floors. Please-remember to give your rabbit a rug or towel made of natural materials (especially rabbits who like to chew) so that the rabbit's feet will not slip or cause any injuries through an inadvertent accident.
Kathleen Bourdelais Rabbit suffering from “head-down syndrome”, the inability to lift the head, reluctance to move and appearance of the third eyelid. On the first day, it also suffered stasis-like signs. Appetite resumed rapidly on the 2^nd day of this syndrome.

It is essential to distinguish between muscle weakness in the neck region and excessive muscle contraction. Typically, neck weakness falls into one of the following categories: motor neuron disease, autoimmune muscle disorder (myasthenia gravis-like), inflammatory muscle disease (polymyositis-like), or idiopathic. Contracted neck muscles, on the other hand, are associated with torticollis or neurotoxins. Given that the flexion of the head is forward and not to the side, it is unrelated to an active infection by Encephalitozoon cuniculi or a middle/inner ear infection.

Despite a thorough physical examination and diagnostic tests, including blood tests, radiography, and a review of the rabbits' medical history, the etiology of this disorder remains uncertain. Veterinarians were unable to identify the cause of this health disorder. What might the cause be?

A few years ago, Rabbit presented with the exact same clinical features and blood chemistry results. Veterinarians were also amazed by his condition: Twilight.

A thorough review of the blood chemistry panel for Midnight and Twilight reveal elevated liver values (AST, ALT, Alk Phosphatase) and a reduced level of phosphorus (hypophosphatemia). Hypophosphatemia has been linked to fulminant hepatic failure and increased metabolism of phosphorus during hepatic function recovery and hepatocyte regeneration. It is hypothesized that the rabbits may have suffered from hepatic encephalopathy, which is a serious condition in which the brain is affected by liver problems. This is thought to be the result of fulminant liver failure and elevated blood ammonia levels.

Blood chemistry panel of Midnight. It shows close parallels with that of another rabbit, Twilight, who suffered a similar disease a few years ago. This could be indicative of hepatic encephalopathy.

(click on the picture to see the full results of the blood test)

Affected rabbits were treated with antibiotics, fenbendazole, and metacam. Treatment consists of supportive care, antibiotics, pain management, and, when necessary, force-feeding. Most animals recover within 7 to 14 days. If necessary, subcutaneous fluids and feeding with a syringe should be initiated. The prognosis is considered guarded to favorable. All affected rabbit made a full recovery within a week.

The following table’s list causes related to difficulties to hold the head high as observed in other including horses, cattle, sheep, and goats. It is possible that further causes exist.

Neurotoxic causes	Many Clostridium sp. bacteria have been found to produce neurotoxins in the blood of infected animals. These conditions can lead to muscle cramps. Botulism, caused by C. botulinum, has been observed in herbivore farm animals. The cause is typically rotten hay. Poor function of the cranial nerves can result in head drops. The condition may be accompanied by weakness in the limbs (flaccid quadriparesis) and decreased reflexes.
	Tick paralysis is a potential complication. Some tick species are known to release toxins in their saliva when biting their host; this includes certain species of Dermacentor sp. in the U.S. and Ixodes holocyclus in Australia. Local paresis (paraparesis) generally progresses to flaccid quadriparesis or quadriplegia, accompanied by weak or absent spinal cord reflexes.
	Black widow spiders release toxins. Muscle weakness can result in ptosis of the head. Some possible symptoms that may accompany this condition are swelling of the eyelids, drooling, pain, and/or difficulty breathing.

Bacterial causes	Pyogranulomatous meningo-encephalomyelitis can result in kyphosis, impaired neck and head mobility, and neck rigidity. The animal exhibits a lack of coordination, including impaired movement and limb function, and a general reluctance to move. If not treated, cervical muscle atrophy is a potential outcome.
	Infection in the spine

Liver disease

Hepatic encephalopathy

Spine abnormalities	Bent spine syndrome
	Ankylosing spondylitis
	Vertebral fracture

Neuropathic or neuromuscular disorders	Myasthenia gravis can result in weakness of the neck muscles. The condition is often accompanied by weakness in the front limbs and difficulty swallowing food.
	Motor neuron disorders
	Reversible demyelinating (poly)neuropathy

Myopathic troubles	Myositis
	Muscle Dystrophy
	Congenital myopathy

Hormonal causes

Hypothyroidism

Mechanical trouble	Trauma
	Presence of a brain or spine tumor

Medication	Certain anti-nausea drugs
	Phenothiazine

The ability to hold the head upright is dependent on the underlying cause and may be reversible or irreversible. Recovery time can vary significantly, ranging from a few days to several months. The prognosis is considered guarded to favorable. The treatment plan includes supportive care, antibiotics, fluid management, pain control, and, when necessary, force-feeding.

I would like to express my gratitude to Kathleen Bourdelais, Suzanne Trayhan and Bonnie Salt for sharing the information about Midnight

and for the permission to use the pictures and videos.

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