How does my jaw move?

The functional anatomy of the jaw is essential to understand dystonic movements of the jaw when a patient is eating or speaking. The chewing movements are extremely complex and I will detail only the main posture of the jaw, following dystonic spasms.

The jaw can move in a vertical plan, with opening or closing the mouth

The jaw can move in a saggital plan, the jaw going forward ( protrusion) or backward ( retrusion)

The jaw can move in a lateral plan, the jaw going side to side or going down and to one side, called deviation of the jaw.

The masticatory muscles, responsible of these movements are 4 pairs of muscles ( masseters, temporalis, median pterygoid and lateral pterygoid muscles) and the mouth floor muscles ( supra-hyoid muscles).

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A combination of these movements is usually involved in the dystonic spams of the jaw. The video recording of a patient when chewing can be very helpful for analysing in details the dystonic spasms.

Dr MH Marion at the London BTX centre, is specialised in the treatment of dystonia, and injects under electromyogram guidance the masticatory muscles involved in oro-mandibular dystonia.

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My jaw is out of control when speaking or chewing: what does it mean?

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                                                    the Iron jaw in circus

Eating is a simple pleasure of life and a necessity. Biting into a biscuit could require a tremendous effort when the movements of the jaw become out of control. The automatic movements of the jaw and the tongue, which allow us to eat or speak, can be disrupted by involuntary jaw spasms.

 

What are the causes of jaw spasms?

1-Idiopathic jaw dystonia is the most common cause of jaw spasms. The onset is between the age of 50 to 60 and it is more frequent in women. Dental works can trigger it. It’s called idiopathic dystonia as no underlying disease can be found. A genetic mutation has been identified in familial form of jaw dystonia ( DYT6).

2-Tardive jaw dystonia can follow a treatment with drugs used for the treatment of psychosis, called neuroleptics.

3- Hereditary disease affecting the brain is often the cause of jaw spasms occuring in young people, under the age of 20.

4- Hemi-masticatory spasms is usually a consequence of radiotherapy of the jaw area for cancer of the ENT sphere. In that case, the spasm is painful and affecting one side of the jaw with sudden, unexpected painful clenching of the jaw.

Are there different types of jaw dystonia?

1-The jaw spasms can be closing spasms with sudden clenching, responsible of tongue biting, teeth breaking and limitation to open the mouth wide

2-The jaw spasms can be opening spasms, responsible of difficulties to keep the mouth closed and to keep the food into the mouth. Often the tongue is involved and has a tendency to poke out the mouth.

3- The jaw spasms can also move involuntary the jaw side to side, or on one side only, or forward (protrusion) or backward (retrusion)

The movement involved in eating and speaking are incredibly complex and the dystonic spasms can be a combination of opening, deviation to one side and going backward or forward.

What are the characteristics of jaw dystonia?

The jaw spasm occurs in any attempts of eating and/or speaking, therefore the diagnosis requires looking at the patient performing these tasks. The doctors should have a box of biscuit available to examine their patients with dystonia!

The spasm are relieved by some tricks like keeping a sweet in the mouth or a chewing gum, sucking a matches or the temples of their spectacles.

How to treat jaw dystonia?

 

The most efficient treatment is the Botox injections of the masticatory muscles.

            -The muscles, which close the jaw, are the masseters, the temporalis and the median pterygoid muscles

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Masseters, closing jaw muscles

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Temporalis, closing jaw muscles

Figure adapted from Travell and Simons’  

-The muscles, which open the mouth, are the lateral pterygoid and the mouth floor muscles.

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Mouth floor muscles ( opening jaw muscles), also called supra-hyoid muscles

Figure adapted from Travell and Simons’

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Median ( closing jaw muscles) and lateral pterygoid (opening jaw muscles)

Figure adapted from Travell and Simons’

‘Some of these muscles are superficial and easy to inject ( masseters, temporalis,mouth floor muscles), some are deeper (median an lateral pterygoid muscles) and requires to be injected with electromyography guidance.

The difficult part is to analyse the abnormal movements and understand which muscles are involved in the dystonia. It can take many injections sessions, to get the spasms under control. The 2 limiting factors are the swallowing difficulties, due to the spread of the Botox , in particular when the tongue  muscles have to be injected.  Starting with small doses and increasing gradually the dosages is advisable.

The human masticatory muscles are very strong, in particular the muscles which closed the mouth; just think of the acrobats in a circus who get suspended by biting a mouthpiece. But at least injecting jaw muscles in human is possible if we compared them to the jaw clamping muscles of the crocodiles, which are extremely strong, and as hard as bone.

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 Strong closing jaw muscles of the crocodiles

Dr Marie-Helene Marion is a specialist in Botox treatment for jaw spasms, and in particular for jaw and tongue dystonia.

Meige syndrome

Henry Meige (1866-1940)

A grimacing face … not an expression of pain or disgust but a neurological condition:

A Meige syndrome

 Forceful dystonic spasms of the face, in particular when trying to speak or to eat have been called Meige syndrome.

 Henry Meige was a French neurologist who published as a junior neurologist, about facial tics with his friend Feindel in 1894 and 2 years later with his maitre Brissaud about neck dystonia, which he is called Torticollis mental (1896). From then, he studied patients with facial movements disorders, not only the tics but what he called “les convulsions de la face”. He also kept a fascination for the spasmodic torticollis that he recognized publically as an organic disease in 1929 after seeing patients suffering from Encephalitis Lethargica and reading the work of Oppenheim (1911) on Dystonia Musculorum Deformans.

In 1910 he described a Bi-blepharospasm (what we call now Blepharospasm) to emphasize that both eyes were affected, with sometimes a positive family history and which could spread to the laryngeal, mouth floor, jaw  and even tongue muscles.

Meige syndrome is now an eponym to describe a blepharospasm associated with a dystonia of the muscles of the lower part of the face and the larynx as described by Meige in 1910. Patients with Meige syndrome are patients over the age of 60, who complains of involuntary eye closure when trying to speak or to chew. The speech or the chewing is affected and the tongue is involuntary pulled out. It usually starts with a blepharospasm, which spreads down in 35 % of the cases to the mouth and the neck. The pattern of activation of the eye closure changes from an isolated blepharospasm which is better when the patient is speaking and worst when the patient is silent to a spasm of eye closure when the mouth is activated.

Meige syndrome has to be treated actively with anticholinergic drugs if tolerated, clonazepam and Botulinum toxin injections into all the dystonic muscles of the face (eyes, jaw, tongue, larynx, neck) ; the facial grimaces can settle and patients with Meige syndrome should keep hope for a better future.

More study is needed to understand the long term prognosis of this condition.

For further reading, I advice you 2 papers from 1976 and 1982 of Professor CD Marsden

Spastic dysphonia,Meige disease and torsion dystonia. CD Marsden, MP Sheehy.1982

http://www.neurology.org/content/32/10/1202.extract

Blepharospasm-oromandibular dystonia syndrome: a form of adult –onset torsion dystonia, CD Marsden, 1976

http://ukpmc.ac.uk/articles/PMC492566/pdf/jnnpsyc00174-0060.pdf