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Patient is a 55 year old woman functionally blind from severe benign essential blepharospasm. She presented with frequent blinking.continuous spasms of eye closure and great difficulty opening her eyes i.e. blepharospasm associated “apraxia of eyelid opening”.
Symptomatic Inquiry negative for tremor of the face, neck or limbs.
Past History negative for neurological disorder, depression or the use of narcoleptic drugs.
Family History negative for blepharospasm, dystonia and neurodegenerative disease.
This patient with severe benign essential blepharospasm (BEB) has active contractions of the orbicularis oculi which prevent eye opening. The eyes not only failing to open, they are being actively squeezed shut.
Electrophysiological investigation of similar patients reconfirms active muscle contraction limited to the pre-tarsal portion of the orbicularis oculi muscle. The term apraxia of eyelid opening is a misnomer and replaced in (ref ) favor of “focal eyelid dystonia”.
For more detail discussion of benign essential blepharospasm/focal dystonia access ID 946-4.
ID 946-4 contains a detailed review of the anatomy of the eyelids and the dynamics of normal eyelid blinking.
Unfortunately for this woman, she presented in the early 1970’s in advance of therapy with botulinum toxin A injections into multiple sites in the upper and lower eyelids.
MRI studies are not done routinely in focal eyelid dystonia.
The dynamics of normal eyelid blinking depends upon a key eyelid muscle – the levator palpebrae superioris muscle which elevates the lid. This muscle, often referred to as the 7th extraocular muscle, is significantly different from the extraocular muscles in that it contains only singly innervated fibres of the types suitable for fatigue resistant tonic activity.
The motor neurons that activate the levator are located in a single midline central caudal nucleus of the 3rd nerve complex in the midbrain and the levator is innervated by the superior branch of the 3rd nerve.
The levator acting alone controls:
1. Tonic lid elevation to keep the eyes open and
2. Voluntary eye closure and eye opening.
Two further muscles, innervated by the facial nerve, act on the eyelid: The frontalis muscle which helps to retract the lid in extreme upward gaze, and the orbicularis oculi muscle which controls periodic and reflex blinking and firm eye closure in protective and expressive acts like sneezing.
In all kinds of blinks the levator is abruptly inhibited to allow the eyes to close and then it resumes its prior level of activity once the contraction of the palpebral portion of the orbicularis oculi, closing the eyelids momentarily, is over. Conversely, the orbicularis oculi activity precedes and outlasts the levator inhibition in firm eye closure.
The brain’s control of the eyelids is major.
The cerebral cortex (R>L) controls the tonic activity of the levator and voluntary eye opening and eye closure.
The dynamics of normal blinks, spontaneous and
voluntary, and the frequency of periodic blinks depend on the affective, attentional and cognitive state of the patient. During sleep and when the eyes are gently closed, activity of the levator ceases completely.
The extrapyramidal dopaminergic circuit influences the execution of blinks and blink frequency and the basal ganglia play a role in the inhibition of the levator during blinks and eye closure.
The fundamental etiology of primary BEB is likely genetic in most cases, even though most cases appear to be sporadic.
Secondary cases of BEB arise as a consequence of a lesion of the brain (Basil Ganglia, Thalamus, and Brain Stem) or they are associate with degenerative CNS disease, including:
Parkinson’s Disease - a dopamine deficiency
Progressive Supranuclear Palsy - a tauopathy
Multiple System Atrophy
Occasionally, secondary BEB occurs as a complication of neuroleptic induced tardive dyskinesia.
As with virtually all neurological degenerative disorders, genetics play a role.
“We don’t know any of the genes that might be responsible for BEB yet. We do know that all the “late life” focal dystonias are related, likely with the same gene since all these dystonias run in some families. (Defazio, etl., 2003a; Defazio et al., 2003b; Defazio et al., 2001) Some families with BEB only have BEB, however, and no other focal dystonia. There is an association with the dopamine D5 receptor in cervical dystonia, and this may be relevant for BEB also. (Brancati et al., 2003) The consequence of the genetic abnormality would be some physiological substrate that would predispose a person to get BEB.” (Personal communication Mark Hallett, MD, 2005)
At present, the speculation is that the late age of onset of BEB and the company that BEB keeps with progressive degenerative CNS disease suggests that this focal dystonic disorder may be secondary to a central disturbance of one or more neurotransmitters and/or synaptic transmission, in genetically predisposed patients.
Benign Essential Blepharospasm - Focal Dystonia "Apraxia" of eyelid opening;
A general recommendation for systemic therapy is to begin an anti-cholinergic drug, slowly building up to a high dose, followed by a trial of baclofen, clonazepam, and then tetrabenazine.
When medical therapy fails, the treatment of choice is Botulinum Toxin A (Botox) injections into multiple (10 – 12) sites in the upper and lower eyelids. If this treatment fails, then myectomy, limited or full, is often the next step.
This patient was seen before Botox was available.