What is Crocodile Tears Syndrome?
The phrase “crocodile tears” comes from an ancient belief that crocodiles shed tears after attacking their prey. A condition called “crocodile tears syndrome,” or Bogorad syndrome, causes people recovering from Bell’s palsy to cry while eating or drinking. This odd reaction is sometimes called gustatory lacrimation.
Understanding the facial nerve is crucial to understanding this syndrome. The facial nerve is responsible for various functions related to movement, sensitivity, and other involuntary actions. The different elements of the facial nerve perform different functions:
- The branchial motor controls facial expressions and certain neck and ear muscles.
- The visceral motor controls tear, saliva, and mucosal glands.
- The special sensory brings taste sensation from the front part of the tongue.
- The general sensory carries sensation from the external ear’s skin.
In the bottom part of the pons (brainstem region), there’s a collection of lower motor neurons called the facial motor nucleus. This structure controls facial expressions and dampens ear vibrations. It receives signals from both hemispheres of the brain to control upper and lower facial muscle groups.
Behind the motor nucleus are the superior salivatory and lacrimatory nuclei. They control salivation and tears, reacting to information from the hypothalamus, taste sensations, and emotional responses. These nuclei also react to irritation in the cornea or conjunctiva, resulting in reflex tear production.
The facial nerve consists of a motor and sensory root that travels with the eighth cranial nerve, combined and divided into three parts to eventually exit the skull. It crosses the stylomastoid process and enters the parotid gland, where it divides into five terminal branches:
- Temporal branches
- Zygomatic branches
- Buccal branches
- Mandibular branch
- Cervical branch
The facial nerve has additional branches within the facial canal for specific tasks. The greater petrosal nerve arises from the geniculate ganglion, carrying signals to the nose, palate, pharynx, and the lacrimal gland, aiding in the production of tears. The nerve to the stapedius serves the function of controlling the stapedius muscle, which prevents the stapes muscle from vibrating excessively. Finally, the chorda tympani carries taste information from the front two-thirds of the tongue to the brain via the middle ear.
Overall, the facial nerve (also referred to as the nervus intermedius), connects to both the submandibular salivary gland and the lacrimal gland, causing it to perform a variety of tasks and signals.
What Causes Crocodile Tears Syndrome?
Crocodile tears syndrome has various proposed explanations. However, the most accepted theory suggests that it’s caused by a condition known as Bell’s palsy, or damage to a specific nerve called the nervus intermedius.
Risk Factors and Frequency for Crocodile Tears Syndrome
Bell palsy is a condition that causes weakness in the facial muscles. This usually happens for reasons that doctors can’t identify. Research has shown that it typically happens to around 0.08% of the population each year, and it becomes more common as people get older, particularly from their 40s to 60s.
- Women are more likely to be affected by Bell palsy than men.
- The left side of the face, specifically the left eye, is usually affected more than the right side.
Sometimes, a complication called Crocodile Tears Syndrome can occur as a result of Bell palsy, though it only happens in about 3.3% of cases. This syndrome typically appears about 6 to 9 months after a person is diagnosed with Bell palsy.
Signs and Symptoms of Crocodile Tears Syndrome
Crocodile tears syndrome is a condition where a person starts tearing up whenever they eat or drink. Most of the time, it only affects one eye, but there have been cases where it’s happened in both eyes. Eye exams, including close-up checks with a medical instrument called a slit lamp, don’t show anything out of the ordinary. This means that the watery eyes aren’t due to other common causes like a blocked tear duct, inflammation of the tear sac, narrow tear duct opening, an eye infection, or something lodged in the eye.
Crocodile tears syndrome is often diagnosed in people who have previously suffered from facial nerve paralysis. People with a history of Bell’s palsy, a type of facial nerve issue, might remember the sudden appearance of neck, mastoid (area of the skull behind the ear), or ear pain, a change in taste or face sensation, and increased sensitivity to sound.
Testing for Crocodile Tears Syndrome
“Crocodile tears syndrome” is a condition that needs to be diagnosed by ruling out other possible causes. This is often done by using a special microscope, called a slit lamp, to closely examine the eye and nearby structures. The Schirmer’s test, which measures how many tears a person makes, can also be used. In people with crocodile tears syndrome, the Schirmer’s test is often done before and after making their mouth water, to show a spike in tears production after salivation.
In addition, certain other conditions need to be excluded:
1. Orbicularis oculi weakness, or a weak muscle around the eye due to facial palsy: This is checked by having the person shut their eyes tightly as the doctor tries to pry them open. The amount of force needed to open the eyelid can be measured, helping understand the severity of the muscle weakness.
2. Paralytic ectropion, or a droopy lower eyelid: The doctor tests this by pulling down the lower eyelid and checking if it quickly snaps back to its normal position.
3. Nasolacrimal duct obstruction, or a blockage in the tear drainage pipe: This is checked using the ROPLAS test, which involves putting pressure on the tear sac to see if it causes a backflow of tears.
Treatment Options for Crocodile Tears Syndrome
In the past, several treatments were used to stop excessive tearing. These included the use of a 5% guanethidine solution, which blocked certain receptors in the tear gland. Other attempts included oral medications and eye drops designed to block nerves related to tear production. However, these treatments often had side effects that outweighed the benefits, so they’re not widely used today.
Some surgical options involved removing parts of the tear gland or cutting specific nerves. Other drastically invasive procedures were used such as using alcohol or cocaine to block a particular ganglion – a mass of nerve cell bodies. These options, though, were often connected with persistent side effects like vision loss and total removal of the tear gland. So, they’re not preferred today either.
Now, the treatment for ‘crocodile tears syndrome’ (a condition of excessive tearing) depends on its severity and the patient’s needs. Mild cases can be managed by counseling and regular checks. Less extreme surgical measures, like partial removal of specific parts of the tear gland, are used and have proven effective.
A widely accepted treatment involves injections of Botulinum toxin (commonly known as Botox) into the tear gland. The toxin acts as a nerve impulse blocker, stopping signals from certain misbehaving nerves to the affected gland. It can be administered through the skin (transcutaneously) or through the mucous membrane lining the eye (transconjunctivally). The effect of the botox typically lasts around six months. Injecting it through the eye lining has fewer complications than through the skin. According to research, this method is safe and effective for treating excessive tearing due to ‘crocodile tears syndrome’.
What else can Crocodile Tears Syndrome be?
When diagnosing ‘Crocodile Tears Syndrome,’ it’s important to first rule out other conditions that could be causing similar symptoms. One such condition is ‘Bell’s Palsy’, which can lead to simple weeping from the eye. This happens because the muscle around the eye loses its strength, causing the lower eyelid to droop. This drooping prevents the normal tears from draining through the small hole at the inner corner of the eye, known as the punctum, leading to watery eyes.
Conjunctivitis (pink eye), allergies, and obstructions in the tear duct can also lead to these symptoms. But it’s worth noting that these conditions are typically not linked to ‘hyperlacrimation’, a condition where there’s excessive tear production particularly during mealtime. In fact, a person with these conditions won’t usually report increased tearing while eating. Furthermore, with Crocodile Tears Syndrome, normal eye examinations typically don’t reveal any abnormality.
Something to keep in mind while diagnosing is that there’s commonly a gap of about six months between the onset of a facial nerve condition, like Bell’s palsy, and the development of Crocodile Tears Syndrome, allowing for the nerves to heal.
