Botulinum toxin improves lid opening delays in blepharospasm-associated apraxia of lid opening

Debunking the Puzzle of Eyelid Apraxia: The Muscle of Riolan Hypothesis

PURPOSE

Apraxia of eyelid opening (AEO) has been defined by the presence of an intermittent nonparalytic bilateral loss of the volitional ability to open the eyes or to maintain the eyelids in a sustained elevated position. It is not known whether the condition represents an apraxia, a dystonia, or a freezing phenomenon, and several different nomenclatorial terms have been suggested for this condition including the so-called AEO (scAEO), blepahrocolysis, focal eyelid dystonia, and so on. The primary goal of this review is to attempt to clarify the pathogenetic mechanisms underlying scAEO as a clinical phenomenon. This review also addresses the issue of whether scAEO is part of the spectrum of blepharospasm (BSP) which includes BSP, dystonic blinks and other dystonic eyelid conditions, or whether it is a separate phenomenologically heterogeneous disease with clinical features that merely overlap with BSP.

METHODS

A literature review was conducted in PubMed, MEDLINE, PubMed Central (PMC), NCBI Bookshelf, and Embase for several related keywords including the terms "apraxia of eyelid opening," "pretarsal blepharospasm," "blepharocolysis," "eyelid freezing," "eyelid akinesia," "levator inhibition," "blepharospasm-plus," as well as "blepharospasm." The clinical findings in patients with scAEO who fulfilled the classic diagnostic criteria of the disease that were originally set by Lepore and Duvoisin were included, while patients with isolated blepharospasm or dystonic blinks (DB) were excluded. In addition, electromyographic (EMG) studies in patients with scAEO were reviewed in detail with special emphasis on studies that performed synchronous EMG recordings both from the levator muscle (LPS) and the pretarsal orbicularis oculi muscle (OO).

RESULTS

The apraxia designation is clearly a misnomer. Although scAEO behaves clinically as a hypotonic freezing phenomenon, it also shares several cardinal features with focal dystonias. The authors broadly categorized the EMG data into 3 different patterns. The first pattern (n = 26/94 [27.6%]) was predominantly associated with involuntary discharges in the OO muscle and has been termed pretarsal blepharospasm (ptBSP). The commonest pattern was pattern no. 2 (n = 53/94 [56.38%]), which was characterized by involuntary discharges in the OO muscle, together with a disturbed reciprocal innervation of the antagonist levator muscle and is dubbed disturbed reciprocal innervation (DRI). This EMG pattern is difficult to discern from the first pattern. Pattern no. 3 (n = 15/94 [15.9%]) is characterized by an isolated levator palpebrae inhibition (ILPI). This levator silence was observed alone without EMG evidence of contractions in the pretarsal orbicularis or a disturbed reciprocal relation of both muscles.

CONCLUSION

EMG evidence shows that the great majority (84%) of patients show a dystonic pattern, whereas ILPI (16%) does not fit the dystonic spectrum. The authors propose that a spasmodic contraction of the muscle of Riolan may be the etiological basis for levator inhibition in patients with ILPI. If this is true, all the 3 EMG patterns observed in scAEO patients (ptBSP, DRI, and ILPI) would represent an atypical form of BSP. The authors suggest coining the terms Riolan muscle BSP ( rmBSP ) for ILPI, and the term atypical focal eyelid dystonia ( AFED ) instead of the term scAEO, as both terms holistically encompass both the clinical and EMG data and concur with the authors' theorem.

Comparison of Botulinum neurotoxin efficiency in dystonia associated with Parkinson's disease and atypical parkinsonism: a retrospective study with a self-reported improvement scale

Botulinum neurotoxin (BoNT) is a useful therapeutic option to treat dystonic manifestations. Data on its efficiency on dystonia associated with Parkinson's disease (PD) or atypical parkinsonism (AP) are scarce and no comparison of the efficiency of BoNT has been performed between these diseases and between the different localizations of dystonia in these pathologies. We retrospectively collected from patients' medical records the result of 611 BoNT injections in 63 dystonic parkinsonian patients (44 PD and 19 AP) using a self-reported clinical improvement scale and duration of effect. Using these data, we modeled the degree of improvement and its duration after BoNT treatment with a linear mixed model. This allowed us to assess the influence of clinical parameters on the reported treatment efficiency. On a scale from 0 to 100, patients with PD and AP, respectively, report a mean improvement of 69% and 55% after BoNT injection and it is similar regarding the different localizations of dystonia. Duration of effect is, however, longer in PD compared to AP (P = 0.023). Patients' demographic and clinical characteristics had no effect on the degree of improvement or duration of effect. Overall, our results support the use of BoNT in the various dystonic phenomena associated with degenerative parkinsonian syndromes. Shorter delays between injection sessions should be considered in AP compared to PD.Trial registration: This study was registered on Clinicaltrial.gov (NCT04948684).

Blink index as a response predictor of blepharospasm to botulinum neurotoxin-A treatment

PURPOSE

We investigated the blink profiles and blink index using ocular surface interferometer in the patients with blepharospasm (BSP) and identified points to consider predictive factor after BSP treatment.

METHODS

In total, 117 eyelids of 59 elderly patients and 20 eyelids of 10 age-matched control group were studied. All BSP patients applied botulinum toxin-A (BoNT-A) injection for treatment of BSP. An ocular surface interferometer (LipiView; TearScience, Morrisville, NC, USA) was used to measure blink profile and blink index; total and incomplete blinks/20 s, and the partial blink ratio (PBR). Eyelid blink time (including lid closing time, closure time, lid opening time), interblink times (IBT), closing speeds (OS), and opening speeds (OS) were analyzed using 600 blinks recorded over 20 s.

RESULTS

Total blink rate was significantly higher in BSP patients compared to the age-matched control group (p = .029) but other time-related and speed-related index including interpalpebral fissure, PBR, blink time, closure time (CT), interblink time, CS, and OS were not significantly different. In the responder of BSP patients, the average age was higher, CT was shorter, CS was faster than nonresponder (age; p = .016, CT; p < .001, CS; p = .042).

CONCLUSION

The blink index by analyzing the blink profile using ocular surface interferometer, and this blink index may be used as a predictive factor for evaluating the clinical response after BoNT-A injection in blepharospasm patients.

Use of Botulinum Neurotoxin in Parkinson's Disease: A Critical Appraisal

For well over 30 years, the botulinum neurotoxin (BoNT) has been used for a large number of indications, some of which however have not been licensed. Admittedly, approval varies in many countries and this permits a large spectrum for evaluation. Thus, BoNT is used for patients with Parkinson’s disease (PD) and other Parkinson’s syndromes (PS) in varying degrees of frequency. We have to distinguish between (1) indications that are either approved or (2) those not approved, (3) indications that might be a result of PS and (4) finally those which appear independent of PS. The most important indication for BoNT in PS patients is probably sialorrhea, for which approval has been granted in the majority of countries. Cervical dystonia is a frequent symptom in PS, with anterocollis as a specific entity. A further indication is blepharospasm in the different forms, especially the inhibition of eyelid opening in atypical PS. The use of BoNT in cases of camptocormia, the Pisa syndrome and neck rigidity is still a matter of debate. In dystonia of the extremities BoNT can be recommended, especially in dystonia of the feet. One well-known indication, for which however sufficient data are still lacking, involves treating tremor with BoNT. As to autonomic symptoms: Focal hyperhidrosis and detrusor hyperactivity can be mentioned, in this last case BoNT has already been approved. A number of further but rare indications such as freezing-of-gait, dyskinesia, and dysphagia will be discussed and evaluated.

Effect of Botulinum Toxin A Treatment on Eyelid Pressure in Eyes with Blepharospasm

OBJECTIVE

To determine the effect of botulinum toxin A (BTX-A) on the eyelid pressure in patients with benign essential blepharospasm (BEB).

METHODS

Twenty normal volunteers (10 men, 10 women; average age 59.7 ± 11.3 years) and 33 patients (12 men, 21 women; average age 61.1 ± 14.7 years) with BEB were studied. The upper and lower eyelid pressures were measured with a blepharo-tensiometer in the normal subjects (N group). The eyelid pressures and intraocular pressures (IOP) were measured before and after the BTX-A injections in the BEB patients (B group).

RESULTS

The mean eyelid pressure in the N group was 31.0 ± 6.8 mmHg for the upper eyelid and 29.9 ± 6.5 mmHg for the lower eyelid (P > 0.05). The mean eyelid pressure in the B group before treatment was 35.3 ± 7.0 mmHg for the upper eyelid and 37.8 ± 6.6 mmHg for the lower eyelid. The eyelid pressure in the B group was significantly higher than in the N group for the upper and lower eyelids (both P < 0.001). The eyelid pressure was significantly decreased after BTX-A treatment for the upper (29.9 ± 7.5 mmHg) and the lower (32.8 ± 7.0 mmHg) eyelids (both P < 0.001). The mean IOP was 15.1 ± 2.9 mmHg before, and it significantly decreased to 14.5 ± 2.8 mmHg (P = 0.020) after the BTX-A injections. The IOP was significantly correlated with the lower eyelid pressure (P = 0.0435), but not with the upper eyelid pressure (P = 0.175).

CONCLUSION

The eyelid pressure was higher in the patients with BEB. The eyelid pressure and the IOP were significantly reduced after the BTX-A injections. In addition, the IOPs were significantly correlated with the eyelid pressure of the lower eyelid.

Neuro-ophthalmology of movement disorders

PURPOSE OF REVIEW

Movement disorders commonly present with ocular features. The purpose of this review is to outline neuro-ophthalmologic findings that can help in diagnosis, treatment and determining prognosis in patients with movement disorders.

RECENT FINDINGS

Common movement disorders with ophthalmic symptoms include extrapyramidal disorders such as Parkinson disease-associated dry eye, decreased blink rate, and vergence dysfunction, and progressive supranuclear palsy-related lid retraction, frequent square-wave jerks and supranuclear gaze palsy. Multisystem atrophy can present with gaze-evoked horizontal or positional downbeat nystagmus and impaired vestibulo-ocular reflex suppression. Genetic disorders such as Huntington disease produce increased saccadic latencies and impaired suppression of saccades to presented stimulus, whereas Wilson disease is associated with saccadic pursuits, increased antisaccade latencies and decreased pursuit gain. Whipple's disease can present with supranuclear gaze palsy and characteristic oculomasticatory myorrhythmia.

SUMMARY

Movement disorders commonly present with ocular features. Knowledge of these ocular symptoms can assist the ophthalmologist in diagnosis and treatment of movement disorders.

Evidence-based review and assessment of botulinum neurotoxin for the treatment of movement disorders

Botulinum neurotoxin (BoNT) can be injected to achieve therapeutic benefit across a large range of clinical conditions. To assess the efficacy and safety of BoNT injections for the treatment of certain movement disorders, including blepharospasm, hemifacial spasm, oromandibular dystonia, cervical dystonia, focal limb dystonias, laryngeal dystonia, tics, and essential tremor, an expert panel reviewed evidence from the published literature. Data sources included English-language studies identified via MEDLINE, EMBASE, CINAHL, Current Contents, and the Cochrane Central Register of Controlled Trials. Evidence tables generated in the 2008 Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (AAN) review of the use of BoNT for movement disorders were also reviewed and updated. The panel evaluated evidence at several levels, supporting BoNT as a class, the serotypes BoNT-A and BoNT-B, as well as the four individual commercially available formulations: abobotulinumtoxinA (A/Abo), onabotulinumtoxinA (A/Ona), incobotulinumtoxinA (A/Inco), and rimabotulinumtoxinB (B/Rima). The panel ultimately made recommendations for each therapeutic indication, based upon the strength of clinical evidence and following the AAN classification scale. For the treatment of blepharospasm, the evidence supported a Level A recommendation for BoNT-A, A/Inco, and A/Ona; a Level B recommendation for A/Abo; and a Level U recommendation for B/Rima. For hemifacial spasm, the evidence supported a Level B recommendation for BoNT-A and A/Ona, a Level C recommendation for A/Abo, and a Level U recommendation for A/Inco and B/Rima. For the treatment of oromandibular dystonia, the evidence supported a Level C recommendation for BoNT-A, A/Abo, and A/Ona, and a Level U recommendation for A/Inco and B/Rima. For the treatment of cervical dystonia, the published evidence supported a Level A recommendation for all four BoNT formulations. For limb dystonia, the available evidence supported a Level B recommendation for both A/Abo and A/Ona, but no published studies were identified for A/Inco or B/Rima, resulting in a Level U recommendation for these two formulations. For adductor laryngeal dystonia, evidence supported a Level C recommendation for the use of A/Ona, but a Level U recommendation was warranted for B/Rima, A/Abo, and A/Inco. For the treatment of focal tics, a Level U recommendation was warranted at this time for all four formulations. For the treatment of tremor, the published evidence supported a level B recommendation for A/Ona, but no published studies were identified for A/Abo, A/Inco, or B/Rima, warranting a Level U recommendation for these three formulations. Further research is needed to address evidence gaps and to evaluate BoNT formulations where currently there is insufficient or conflicting clinical data.

Uses of Botulinum Toxin a in Ophthalmology

Introduction:

Botox® (serotype A) is currently available and used to treat various ophthalmological conditions. The aim of our study was to review the current indications, side-effects and updates on the clinical use of botulinum toxin- A (Btx-A) in the field of ophthalmology.

Methods:

A literature search using the keywords “Botulinum Toxin”, “Botulinum Toxin A”, “Botox” and “Ophthalmology” was performed using Pubmed. Articles describing the use of botulinum toxin A were selected and reviewed.

Results:

The uses of Btx-A in ophthalmology can be broadly classified into four categories: eyelid, strabismus, cosmetic and others. In the eyelid, it can be used to treat blepharospasm, hemifacial spasm, apraxia of lid opening or induce ptosis in lid retraction and exposure keratopathy. In strabismus management, it can be injected into overacting muscles to realign the eyes. For cosmesis, it can be used to relax facial muscles to reduce wrinkles while other indications include treatment of chronic dry eye, lacrimal hypersecretion and pain relief in acute angle closure attack. Complications of the injection include local effects like ecchymosis, pain or infection and spillover effects like ptosis, diplopia, lagophthalmos, mid facial weakness and dry eyes.

Conclusion:

The clinical application of botulinum toxin A in ophthalmology is extensive. When considering its application in clinical practice, one should be mindful of the indications, risks and benefits of the procedure. When properly delivered, its potential as an efficacious, minimally-invasive treatment modality can be maximised in patient management.

Noncosmetic periocular therapeutic applications of botulinum toxin

Botulinum toxin blocks acetylcholine release at the neuromuscular junction. The drug which was initially found to be useful in the treatment of strabismus has been extremely effective in the treatment of variety of conditions, both cosmetic and noncosmetic. Some of the noncosmetic uses of botulinum toxin applications include treatment of spastic facial dystonias, temporary treatment of idiopathic or thyroid dysfunction-induced upper eyelid retraction, suppression of undesired hyperlacrimation, induction of temporary ptosis by chemodenervation in facial paralysis, and correction of lower eyelid spastic entropion. Additional periocular uses include control of synchronic eyelid and extraocular muscle movements after aberrant regeneration of cranial nerve palsies. Cosmetic effects of botulinum toxin were discovered accidentally during treatments of facial dystonias. Some of the emerging nonperiocular application for the drug includes treatment of hyperhidrosis, migraine, tension-type headaches, and paralytic spasticity. Some of the undesired side effects of periocular applications of botulinum toxin inlcude ecchymosis, rash, hematoma, headache, flu-like symptoms, nausea, dizziness, loss of facial expression, lower eyelid laxity, dermatochalasis, ectropion, epiphora, eyebrow and eyelid ptosis, lagophthalmos, keratitis sicca, and diplopia.

Treatments for neuro-ophthalmologic conditions

Neuro-ophthalmology covers disorders that fall between the cracks of Neurology and Ophthalmology. Neurologists see patients with neuro-ophthalmic disorders. Recognition of the diagnosis is difficult enough, but treatment can be challenging. This article reviews several common neuro-ophthalmic disorders, outlining their features and treatments, from retinal vascular disorders to eye movements and blepharospasm.

Review and update of involuntary facial movement disorders presenting in the ophthalmological setting

We review the existing literature on the involuntary facial movement disorders-benign essential blepharospasm, apraxia of eyelid opening, hemifacial spasm, and aberrant facial nerve regeneration. The etiology of idiopathic blepharospasm, a disorder of the central nervous system, and hemifacial spasm, a condition involving the facial nerve of the peripheral nervous system, is markedly different. We discuss established methods of managing patients and highlight new approaches.

Apraxia of lid opening mimicking ptosis in compound heterozygosity for A467T and W748S POLG1 mutations

Patients harboring A467T and W748S POLG1 mutations present with a broad variety of neurological phenotypes, including cerebellar ataxia, progressive external ophthalmoplegia (PEO), myoclonus, epilepsy, and peripheral neuropathy. With exception of ataxia and myoclonus, movement disorders are not typical features of POLG1 associated disorders. We report on two affected siblings compound heterozygous for A467T and W748S mutations, one suffering from choreoathetosis and apraxia of lid opening due to focal eyelid dystonia that mimicked progression of ptosis, resulting in functional blindness. So far, focal dystonia has not been reported in POLG1 mutation carriers, and should be considered when investigating patients with PEO and ptosis. Further studies on POLG1 mutations in focal dystonia are warranted.

Upper eyelid myectomy in blepharospasm with associated apraxia of lid opening

PURPOSE

To assess the impact of upper eyelid myectomy surgery on blepharospasm with associated apraxia of lid opening (ALO), dry eye, photophobia, and daily functioning in patients who are refractory to botulinum toxin treatment.

DESIGN

Noncomparative, consecutive, interventional case series.

METHODS

A retrospective chart review was performed to identify 100 consecutive patients beginning on January 1, 2000, who underwent upper eyelid myectomy surgery for blepharospasm and fulfilled the inclusion criteria. A survey was sent to all patients. Data were entered in an anonymous manner into a spreadsheet and analysis was performed using the Student t test with significance set at P<.05.

RESULTS

Forty-five (88%) patients experienced ALO before surgery, among which 15 (33%) patients stated they were completely cured and 20 (44%) others had more than 50% improvement in ALO with surgery. In 20 of 30 patients who continued botulinum toxin treatment after surgery, the effect lasted longer. Twelve (29%) of 42 patients who experienced dry eyes before surgery improved. Eighteen (41%) of the 44 patients who experienced light sensitivity before surgery improved. Thirty-seven (82%) patients noted their cosmetic appearance to be better after surgery. The cumulative preoperative disability score was 14.11+/-5.78 (59%), whereas the cumulative postoperative disability score was 5.20+/-8.25 (22%; P<.01).

CONCLUSIONS

Upper eyelid myectomy surgery appears to be effective in treating blepharospasm with associated ALO in most patients who are refractory to botulinum toxin injections and can provide improvement in the quality of life.

Botulinum toxin in the treatment of tremors, dystonias, sialorrhea and other symptoms associated with Parkinson's disease

Botulinum toxins are an effective treatment modality for a growing number of neurologic conditions. Although there has been varied interest and success in their use, they have been studied for a variety of conditions associated with Parkinson's disease. Conditions reviewed in this paper include hand and jaw tremor, dystonia, blepharospasm and apraxia of eyelid opening, bruxism, camptocormia, freezing of gait, sialorrhea and constipation. We will make comments when applicable on our unique experience with botulinum toxin in these conditions. Other conditions associated with Parkinson's disease, which will not be reviewed here, but may benefit from botulinum toxin treatment include anterocollis (also known as dropped head syndrome), hyperhidrosis, seborrhea and overactive bladder.

Botulinum toxin injection into Riolan's muscle: somatosensory 'trick'

We studied the effect of injecting botulinum toxin A (BTX-A) into the pars ciliaris--also known as Riolan's muscle--of patients with eyelid apraxia (ELA). Six patients with ELA were treated with injections of BTX-A into the region of Riolan's muscle at the medial and lateral portions of the upper and lower pretarsal orbicularis oculi. Clinical benefit was seen in all 6 patients, 2 of whom had previously been treated with conventional pretarsal injections of BTX-A and had not improved. BTX-A injections into Riolan's muscle are effective as treatment for ELA. The proposed mechanism is not that of muscle relaxation but rather modulation of the somatosensory cortex, similar to that of a 'sensory trick' in patients with dystonia.

Modified Lundie loops improve apraxia of eyelid opening

BACKGROUND

Current treatments are unsatisfactory for improving apraxia of eyelid opening, defined as a delay or inability to open closed eyelids voluntarily in the presence of intact motor pathways.

METHODS

Improvement in functional health was assessed using the Blepharospasm Disability Scale (BDS) in five consecutive patients with apraxia of eyelid opening treated with wire loops affixed behind ordinary spectacles (Lundie loops) and modified to provide pressure on the brow as a stimulus to keep the eyelids elevated.

RESULTS

All five patients showed improvement in BDS scores. The mean percentage of normal activity of the study population improved from 25% to 37.6%. Outdoor activities were not significantly altered with the use of the device.

CONCLUSIONS

Modified Lundie loops appear to be helpful in improving the functional health of patients with eyelid apraxia. These results will need to be verified in larger trials.

Botulinum Toxin in Ophthalmology

Since its introduction into clinical medicine in 1980, botulinum toxin has become a major therapeutic drug with applications valuable to many medical sub-specialties. Its use was spearheaded in ophthalmology where its potential applications have expanded to cover a broad range of visually related disorders. These include dystonic movement disorders, strabismus, nystagmus, headache syndromes such as migraine, lacrimal hypersecretion syndromes, eyelid retraction, spastic entropion, compressive optic neuropathy, and, more recently, periorbital aesthetic uses. Botulinum toxin is a potent neurotoxin that blocks the release of acetylcholine at the neuromuscular junction of cholinergic nerves. When used appropriately it will weaken the force of muscular contraction, or inhibit glandular secretion. Recovery occurs over 3 to 4 months from nerve terminal sprouting and regeneration of inactivated proteins necessary for degranualtion of acetylcholine vesicles. Complications are related to chemodenervation of adjacent muscle groups, injection technique, and immunological mechanisms.

Treatment of dystonia

Dystonia may be a sign or symptom, that is comprised of complex abnormal and dynamic movements of different etiologies. A specific cause is identified in approximately 28% of patients, which only occasionally results in specific treatment. In most cases, treatment is symptomatic and designed to relieve involuntary movements, improve posture and function and reduce associated pain. Therapeutic options are dictated by clinical assessment of the topography of dystonia, severity of abnormal movements, functional impairment and progression of disease and consists of pharmacological, surgical and supportive approaches. Several advances have been made in treatment with newer medications, availability of different forms of botulinum toxin and globus pallidus deep brain stimulation (DBS). For patients with childhood-onset dystonia, the majority of whom later develop generalized dystonia, oral medication is the mainstay of therapy. Recently, DBS has emerged as an effective alternative therapy. Botulinum toxin is usually the treatment of choice for those with adult-onset primary dystonia in which dystonia usually remains focal. In patients with secondary dystonia, treatment is challenging and efficacy is typically incomplete and partially limited by side effects. Despite these treatment options, many patients with dystonia experience only partial benefit and continue to suffer significant disability. Therefore, more research is needed to better understand the underlying cause and pathophysiology of dystonia and to explore newer medications and surgical techniques for its treatment.

Deep brain stimulation: Postoperative issues

Numerous factors need to be taken into account when managing a patient with Parkinson's disease (PD) after deep brain stimulation (DBS). Questions such as when to begin programming, how to conduct a programming screen, how to assess the effects of programming, and how to titrate stimulation and medication for each of the targeted sites need to be addressed. Follow-up care should be determined, including patient adjustments of stimulation, timing of follow-up visits and telephone contact with the patient, and stimulation and medication conditions during the follow-up assessments. A management plan for problems that can arise after DBS such as weight gain, dyskinesia, axial symptoms, speech dysfunction, muscle contractions, paresthesia, eyelid, ocular and visual disturbances, and behavioral and cognitive problems should be developed. Long-term complications such as infection or erosion, loss of effect, intermittent stimulation, tolerance, and pain or discomfort can develop and need to be managed. Other factors that need consideration are social and job-related factors, development of dementia, general medical issues, and lifestyle changes. This report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society, outlines answers to a series of questions developed to address all aspects of DBS postoperative management and decision-making with a systematic overview of the literature (until mid-2004) and by the expert opinion of the authors. The report has been endorsed by the Scientific Issues Committee of the Movement Disorder Society and the American Society of Stereotactic and Functional Neurosurgery.

Botulinum neurotoxin type A causes shifts in myosin heavy chain composition in muscle

Botulinum neurotoxin type A has gained widespread use for treatment of a host of neuromuscular conditions. However, the potential effect of this toxin has on the histological and biochemical properties of skeletal muscle remains largely unexplored. The purpose of this study was to characterize the myosin heavy chain (MHC) distribution of adult rat skeletal muscle treated with botulinum neurotoxin type. Varying doses of the toxin were injected into the triceps surae muscle group of one hind limb. Force production was assessed periodically to access the functional deficit incurred. After 10 weeks, animals were sacrificed, muscles removed, and MHC composition determined. Body weight, muscle weight and force of the injected leg were significantly reduced in all groups, while loss of muscle weight and force in the contralateral leg was variable. In the injected plantaris and gastrocnemius muscles, type I MHC increased approximately 100%, while type IIa/x decreased approximately 50%. In the contralateral gastrocnemius, types I and IIa/x MHC increased approximately 100%, while type IIb decreased approximately 45%. These data suggest that botulinum neurotoxin causes shifts in MHC composition in injected and contralateral muscles that are contrary to those seen with denervation and similar to those seen with aging.

Primary Blepharospasm

Primary blepharospasm is an adult-onset focal dystonia characterised by involuntary contractions of the orbicularis oculi muscles. Patients may have various types of movements arising from the different parts of the orbicularis oculi muscle. These include typical blepharospasm associated with Charcot's sign, pretarsal blepharospasm and flickering of the eyelids. Primary blepharospasm may be associated with so-called apraxia of eyelid opening as well as dystonia in the lower face, jaw or cervical muscles. Unless there are clinical clues to a symptomatic cause, adults presenting with blepharospasm do not require extensive aetiological investigation because the condition is rarely due to an identifiable condition. As the aetiology of primary blepharospasm is largely unknown, therapeutic approaches are symptomatic, with type A botulinum toxin being the treatment of choice.