Masseter hypertrophy is a rare condition. It is mostly idiopathic with no known cause. It is recognized as an enlargement of one or both masseter muscles. Most patients complain of facial asymmetry; however, symptoms such as trismus, protrusion, and bruxism may also occur. This article reports a case of bilateral masseter hypertrophy with retrognathic mandible in which comprehensive treatment was rendered to the patient by using a combination approach.
Masseteric hypertrophy; orthognathic surgery; sagittal split osteotomy
Intramuscular hemangiomas are uncommon neoplasm's arising most frequently in the masseter and trapezius muscle. Due to it's location it is often mistaken for a parotid swelling and rarely is an accurate pre-operative diagnosis achieved clinically. The intra masseteric location also poses special problem in terms of proximity to the facial nerve and the post operative flattening following excision of the masseter muscle. A case of intramuscular hemangioma in a 17 year old girl is presented. Inadequacy of computed tomography scan and cytology in achieving a pre-operative diagnosis and also the treatment modalities are reviewed here. An estrogen receptor and progesterone receptor study has been done to verify the hormonal basis of this tumour.
Experiments were carried out on seven adult subjects in order to establish the relationship between the magnitude of the masseteric reflex and the amount of voluntary activity present in the muscle at the time the reflex was evoked. At the same time, an effort was made to determine whether the magnitude of the reflex could be enhanced by the simultaneous voluntary contraction of muscles other than that being tested (the Jendrassik manoeuvre). The reflex was evoked by applying controlled downward thrusts to the mandible so as to produce a constant displacement in each case, and the response of the masseter muscle was recorded by means of small bipolar surface electrodes attached to the skin over the muscle. These responses were averaged by a computer in the presence of various static loads supported by the mandible. It was found that in all subjects the amplitude of the masseteric reflex appeared to increase as the weight supported by the mandible increased, and that in the majority of subjects it was possible to demonstrate Jendrassik facilitation by simultaneous contraction of the muscles of the upper limbs. The results of the experiments suggest that the enhancement of the masseteric reflex by voluntary contraction of the jaw-closing muscles may be due to autogenetic factors, synergistic factors, or both, and that at least two processes contribute to the amplitude of the masseteric reflex evoked by tooth contact during mastication—namely, the stimulation of muscle spindles by the impact of opposing teeth and facilitation caused by voluntary activity in the jaw-closing muscles before tooth contact.
Paralysis of the masticatory muscles using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters as well as for conditions involving muscle spasm and pain. The effects of this treatment on mastication have not been evaluated, and claims that the treatment unloads the jaw joint and mandible have not been validated. If BTX treatment does decrease mandibular loading, osteopenia might ensue as an adverse result. Rabbits received a single dose of BTX or saline into one randomly chosen masseter muscle and were followed for 4 or 12 weeks. Masticatory muscle activity was assessed weekly, and incisor bite force elicited by stimulation of each masseter was measured periodically. At the endpoint, strain gages were installed on the neck of the mandibular condyle and on the molar area of the mandible for in vivo bone strain recording during mastication and muscle stimulation. After termination, muscles were weighed and mandibular segments were scanned with micro CT. BTX paralysis of one masseter did not alter chewing side or rate, in part because of compensation by the medial pterygoid muscle. Masseter-induced bite force was dramatically decreased. Analysis of bone strain data suggested that at 4 weeks, the mandibular condyle of the BTX-injected side was underloaded, as were both sides of the molar area. Bone quantity and quality were severely decreased specifically at these underloaded locations, especially the injection-side condylar head. At 12 weeks, most functional parameters were near their pre-injection levels, but the injected masseter still exhibited atrophy and percent bone area was still low in the condylar head. In conclusion, although the performance of mastication was only minimally harmed by BTX paralysis of the masseter, the resulting underloading was sufficient to cause notable and persistent bone loss, particularly at the temporomandibular joint.
Botulinum neurotoxin; masseter; mastication; mandibular bone strain; bone microarchitecture; temporomandibular joint
Lymphangioma is a rare benign condition characterized by proliferation of lymphatic spaces. It is usually found in the head and neck of affected children. Lymphangioma of the small-bowel mesentery is rare, having been reported for less than 1% of all lymphangiomas. Importantly, it can cause fatal complications such as volvulus or involvement of the main branch of the mesenteric arteries, requiring emergency surgery. Moreover, the gross and histopathologic findings may resemble benign multicystic mesothelioma and lymphangiomyoma. Immunohistochemical study for factor VIII-related antigen, D2-40, calretinin and human melanoma black-45 (HMB-45) are essential for diagnosis. Factor VIII-related antigen and D2-40 are positive in lymphangioma but negative in benign multicystic mesothelioma. HMB-45 shows positive study in the smooth-muscle cells around the lymphatic spaces of the lymphangiomyoma. We report a case of small-bowel volvulus induced by mesenteric lymphangioma in a 2-year-and-9-mo-old boy who presented with rapid abdominal distension and vomiting. The abdominal computed tomography scan showed a multiseptated mass at the right lower quadrant with a whirl-like small-bowel dilatation, suggestive of a mesenteric cyst with midgut volvulus. The intraoperative findings revealed a huge, lobulated, yellowish pink, cystic mass measuring 20 cm × 20 cm × 10 cm, that was originated from the small bowel mesentery with small-bowel volvulus and small-bowel dilatation. Cut surface of the mass revealed multicystic spaces containing a milky white fluid. The patient underwent tumor removal with small-bowel resection and end-to-end anastomosis. Microscopic examination revealed that the cystic walls were lined with flat endothelial cells and comprised of smooth muscle in the walls. The flat endothelial cells were positive for factor VIII-related antigen and D2-40 but negative for calretinin. HMB-45 showed negative study in the smooth-muscle cells around the lymphatic spaces. Thus, the diagnosis was lymphangioma of the small bowel mesentery with associated small bowel volvulus.
Lymphangioma; Mesentery; Small bowel; Volvulus; Factor VIII-related antigen; D2-40
This case report describes a patient with nocturnal bruxism and related neck pain treated with botulinum toxin type A (BTX-A).
The patient was a 27-year-old man with nocturnal bruxism and difficulty in active mouth opening and chewing and neck pain at rest. His numeric pain score was 7 of 10. Surface electromyography of the temporalis and masseter muscles showed typical signs of hyperactivity, characterized by compound muscle action potential amplitude alterations.
Intervention and Outcome
After clinical evaluation, he was treated with BTX-A to reduce masseter and temporalis muscle hyperactivity. After 3 days of treatment with BTX-A, with each masseter muscle injected with a dose of about 40 mouse units with a dilution of 1 mL and with temporal muscle bilaterally injected with 25 mouse units with the same dilution, a decrease in bruxism symptoms was reported. Neck pain also decreased after the first treatment (visual analog scale of 2/10) and then resolved completely. After 4 weeks, electromyography showed the reduction of muscle hyperactivity with a decrease in the amplitude of the motor action potential. The same reduction in signs and symptoms was still present at assessment 3 months posttreatment.
These findings suggest that BTX-A may be a therapeutic option for the treatment of bruxism and related disorders.
EES: bruxism; Neck pain; Botulinum toxin type A
Sleep bruxism has been described as a combination of different orofacial motor activities that include grinding, clenching and tapping, although accurate distribution of the activities still remains to be clarified.
We developed a new system for analyzing sleep bruxism to examine the muscle activities and mandibular movement patterns during sleep bruxism. The system consisted of a 2-axis accelerometer, electroencephalography and electromyography. Nineteen healthy volunteers were recruited and screened to evaluate sleep bruxism in the sleep laboratory.
The new system could easily distinguish the different patterns of bruxism movement of the mandible and the body movement. Results showed that grinding (59.5%) was most common, followed by clenching (35.6%) based on relative activity to maximum voluntary contraction (%MVC), whereas tapping was only (4.9%).
It was concluded that the tapping, clenching, and grinding movement of the mandible could be effectively differentiated by the new system and sleep bruxism was predominantly perceived as clenching and grinding, which varied between individuals.
Hereditary multiple exostoses (HME) is a dominantly inherited skeletal disorder which alters enchondral bone during growth and is characterized by exostoses of the juxta-epiphyseal regions. These exostoses are benign cartilaginous neoplasms that consist of a pedicle of normal bone covered with proliferating cartilage cells. Pathologic, clinical, and radiographic findings are discussed and a case of a nine-year-old male is reviewed.
hereditary multiple exostoses; painful joints; bony masses; chiropractic
Introduction: The present study was designed to clarify whether the bilateral cooperation in the human periodontal-masseteric reflex (PMR) differs between central incisors and canines. Methods: Surface array electrodes were placed on the bilateral masseter muscles to simultaneously record the firing activities of single motor units from both sides in seven healthy adults. During light clenching, mechanical stimulation was applied to the right maxillary central incisor and canine to evoke the PMR. Unitary activity was plotted with respect to the background activity and firing frequency. The slope of the regression line (sRL) and the correlation coefficient (CC) between the central incisor and canine and the lateral differences between these values were compared. Results: There were significant differences in the sRL and CC, as well as lateral differences, between the central incisor- and canine-driven PMR. Discussion: These results suggest that the PMR differs depending on both the tooth position and laterality.
periodontal-masseteric reflex; mechanoreceptor; motor unit; teeth; human
Craniofacial muscle pain including muscular temporomandibular disorders accounts for a substantial portion of all pain perceived in the head and neck region. In spite of its high clinical prevalence, the mechanisms of chronic craniofacial muscle pain are not well understood. Injection of acidic saline into rodent hindlimb muscles produces pathologies which resemble muscular pathologies in chronic pain patients. Here we investigated whether analogous transformations occur following repeated injections of acidic saline into the rat masseter muscle. Injection of acidic saline (pH 4) into the masseter muscle transiently lowered intramuscular pH to levels comparable to those reported for rodent hindlimb muscles. Nevertheless, repeated unilateral or bilateral injections of acidic saline (pH 4) into the masseter muscle failed to alter nociceptive behavioral responses as occurs in the hindlimb. Changing the pH of injected saline to pH 3.0 or 5.0 also did not evoke nocifensive behavior. ASIC3 receptors, which are implicated in transformations following acidification of hindlimb muscles, were found on trigeminal ganglion muscle afferent neurons via combined neuronal tracing and immunocytochemistry. In contrast to the acidic saline, injection of complete Freund’s adjuvant (CFA) into the masseter muscle induced mechanical allodynia for three weeks, thermal hyperalgesia for one week and an increase in the number of CGRP-immunoreactive muscle afferent neurons in the trigeminal ganglion. Although pH may alter CGRP release in primary afferent neurons, the number of CGRP-muscle afferent neurons did not change following intramuscular injection of acidic saline. Further, there was no change in ganglionic iCGRP levels at one, four or twelve days after intramuscular injection of acidic saline. While these findings extend our earlier reports that CFA-induced muscle inflammation results in behavioral and neuropeptide changes they further suggest that intramuscular acidification in craniofacial muscle evokes different responses than in hindlimb muscle and imply that disparate proton sensing mechanisms underlie these discrepancies.
pain; trigeminal; pH; chronic; deep tissue; TMD
The aim of this study is to show that a change in occlusal contacting pattern of tooth has definite influence over the behavior of orofacial musculature, resulting deleterious effect on it. Keeping this in view, the electromyographic (EMG) activity of temporalis and masseter muscles in rest position of mandible, maximum clenching and chewing, was studied in total 24 subjects--14 subjects with normal occlusion and rest 10 with normal occlusion and one tooth carious which was prepared to receive an inlay with high point. This high point or occlusal interference was introduced intentionally to have a change in occlusion or “altered dentition”. The subjects were all male medical volunteers with average age group of 20 years. A particular variety of chewing substance – chewing gum was used in this study. No EMG activity was detected in the rest position of mandible. In maximum clenching, balanced type of activity was seen bilaterally in normal occlusion. Whereas in changed occlusion, an unbalanced type of muscle activity was seen in temporalis muscle during maximum clenching. There was an overall decrease in activity in both the muscles during maximum clenching and during chewing. This decrease in activity was statistically significant in most of the times. A non-specific pattern of muscle activity resembling spasm in skeletal muscle -- a state of “hyperactivity” was also found during chewing in presence of occlusal interference. This spasm-like activity may cause pain in the muscles of masticatory apparatus. All these abnormal types of behavior of muscle were abolished after removal of high point and establishing the previous normal occlusion. It is therefore, for the clinicians to understand the importance of establishing occlusal equilibrium in day to day practice.
Altered dentition; EMG pattern; masticatory
Lymphangiomas are benign lesions that are most commonly encountered in the neck of small infants, but are quite uncommon in the adult population. Their removal can be quite difficult, when they reach enormous dimensions or they develop in critical locations. Complete resection is curative, but incomplete resections entail the risk of relapse. Lymphangiomas of the chest wall are quite rare.
PRESENTATION OF CASE
We report a case of a 35-year old man with a giant cavernous lymphangioma of the right lateral chest wall extending into the axilla, which was removed en bloc.
These tumors of lymphatic origin tend to grow, as is the case in our patient, but they also tend to recur if not resected completely. Clinical examination and chest CT scan may provide a clue to the diagnosis.
Lymphangiomas of the thoracic wall are extremely rare lesions and wide resection is recommended due to the high recurrence rate of these benign lesions.
Adult; Chest wall; Lymphangiomatous cysts; Chest wall tumors
The jaw-jerk response was elicited in seven adult male subjects by tapping on the chin in a downward direction. The magnitude of the applied taps was varied subjectively by the operator, and the downward acceleration of the mandible measured by means of a calibrated piezo-electric accelerometer fixed to the lower anterior teeth. The taps were applied during voluntary clenching by the subject, controlled by means of a force transducer placed between upper and lower teeth. The electrical response of masseter and temporal muscles was found to increase both with increasing stimulus strength and with voluntary clenching force. However, only by averaging a number of responses were clear relationships demonstrated, there being other variables, affecting the muscles independently, which it has not been possible to identify and control. It is concluded therefore, that quantitative analysis of the electromyograms of the jaw closing muscles following chin-tap stimuli is not a satisfactory method for testing for abnormality in excitability of the neuromuscular system involved in the jaw-jerk response.
Benign mesenteric lymphangiomas are rare intra-abdominal cysts which may be asymptomatic or present with a variety of abdominal symptoms including an acute abdomen. We are however not aware of any reports in the literature linking mesenteric lymphangioma to acute pancreatitis. We present the case of a 62-year-old man who was admitted with signs and symptoms of acute pancreatitis and a palpable abdominal mass. Computerised tomography (CT) of his abdomen confirmed the presence of a mesenteric cystic mass. He underwent a laparotomy at which a large thin walled mass filled with a chylous fluid was resected. Histological analysis of this cyst showed it to be a benign mesenteric lymphangioma.
Background and aims
Temporomandibular disorders (TMDs) are the most common condition affecting the tem-poromandibular joint and associated structures. The aim of this study was the epidemiologic evaluation of TMDs and re-lated factors in a group of Iranian adolescents.
Materials and methods
This descriptive cross-sectional survey included a sample of800 high school students (400 girls and 400 boys) aged 14 to18 years, in Mashhad, Iran, selected using cluster sampling. Examiners completed question-naires and performed the clinical examinations. Data were analyzed with the Chi-square and Fisher exact tests.
The prevalence of TMDs in the studied sample was 34.7%. The most common signs of TMDs were clicking, muscle tenderness and TMJ tenderness. The most prevalent predisposing factors of TMDs were clenching, premature con-tact in protrusive movement and bruxism. A clear predominance was seen in girls (40.5%) compared with boys (29%) (P = 0.001).
Signs and symptoms of TMDs were prevalent in Iranian adolescents with a clear female predominance.
Adolescent; epidemiology; temporomandibular joint disorders
Lymphangioma is a benign and congenital malformation of the lymphatic system. Most lymphangiomas are preferentially located in the head and neck region. The abdominal organs are uncommon sites of origin. Several cases of lymphangioma in abdominal organs were reported, however, the pancreas is one of the rarest origins. Generally, intra-abdominal lymphangioma is asymptomatic and found incidentally, but in some cases, the patient complains of abdominal distension or a palpable mass. We describe the case of a 38-year-old male who presented with sudden-onset upper abdominal pain. Rupture of a cystic tumor of the pancreatic head was suspected, based on the findings of computed tomography, magnetic resonance imaging and endoscopic ultrasonography. Subtotal stomach-preserving pancreaticoduodenectomy was undertaken. The tumor, which was 4 × 4.5 × 8 cm in size, was pathologically diagnosed as a cystic lymphangioma. In conclusion, pancreatic lymphangioma is mostly asymptomatic, a ruptured case causing ‘acute abdomen’ has never been reported. Since lymphangioma is benign, it could be observed with accurate diagnosis. The surgical indication would be limited to cases of symptomatic lymphangiomas.
Lymphangioma; Pancreas; Rupture; D2-40
Abdominal cystic lymphangiomas are uncommon congenital benign tumors.
We present a case of a 4 year old female child with a cystic lymphangioma arising from greater omentum and occupying whole of the abdomen and protruding through labia mejora. Ultrasonography and CT scan confirmed the diagnosis. Complete excision of the cyst along with omentectomy done with no clinical or radiological evidence of recurrence till 6 months.
Due to variable presentation of abdominal lymphangiomas, extensive imaging studies are necessary for evaluation and diagnosis. Complete surgical resection is a treatment of choice.
Lymphangioma is an uncommon benign lesion that usually occurs during childhood. Its occurrence in adults is rare. Its presentation in the abdomen is even rare. This case report describes a case of omental lymphangioma presented as retroperitoneal lump. Subsequent imaging, operative, and histological findings revealed omental lymphangioma. Laparotomy done under general anesthesia, a 10 × 12 cm cystic swelling arising from omentum, identified complete excision of the cyst done and send the specimen for histopathological examination. Biopsy report came as omental lymphangioma. Complete surgical excision is the treatment of choice. Prognosis is excellent and recurrence rate is very low if resection is complete. During two years of followup no recurrence was detected. Omental lymphangioma is very rare presentation among abdominal lymphangiomas specifically in adults. Complete excision is the treatment of choice. Long-term followup is required to detect recurrence.
Lymphangioma circumscriptum is a rare benign skin disorder involving hamartomatous lymphatic malformation of deep dermal and subcutaneous lymphatic channels. It is a therapeutic challenge for the dermatologist when it occurs at common sites such as axilla, shoulder, groin and buttocks and a diagnostic challenge for the surgeon when it occurs at rare sites such as the scrotum. Surgical treatment is the most commonly used method to treat scrotal lymphangioma circumscriptum but there are high rates of recurrence.
We report the case of a 30-year-old Pakistani man who presented with scrotal swelling which was clinically misinterpreted as an infectious disorder. Later on re-resection of deeper tissue was performed to prevent recurrence. He is still being followed-up on a regular basis.
Awareness of the occurrence of lymphangioma circumscriptum in the scrotum in adult men without prior disease is mandatory to avoid missing the diagnosis and to ensure proper treatment.
Follow-up; Lymphangioma circumscriptum; Scrotum; Surgical treatment
Lymphangiomas are benign hamartomatous lymphatic tumors. The mainstay of the therapy is surgical excision, but due to its infiltration along the nerves and muscles, total excision is not always possible. In the present study, we have evaluated the clinical profile of all the cases of lymphagiomas coming to our department and evaluated the efficacy of intralesional Bleomycin as a sclerosing agent in its management.
Materials and Methods:
In this prospective study, all patients were evaluated clinically and color Doppler ultrasonography (USG). The required dose was calculated as 0.5 mg/kg body weight, not exceeding 10 units at a time. The response was assessed clinically and on the basis of color Doppler USG.
Thirty-five patients of lymphangioma were included in the study. The neck region was the most common site of involvement. The response was excellent in 7 (20%), good in 26 (74.29%), and poor in 2 (5.71%) patients. The complications included fever, transient increase in size of swelling, local infection, intraluminal bleed, and skin discoloration in 10 patients.
This therapy may be used as primary modality instead of surgery in selected group of patients.
Bleomycin; intralesional bleomycin; lymphangioma; surgery
A major subgroup of patients with temporomandibular joint (TMJ) disorders have masticatory muscle hypersensitivity. To study myofacial temporomandibular pain, a number of preclinical models have been developed to induce myogenic pain of the masseter muscle, one of the four muscles involved in mastication. The currently used models, however, generate pain that decreases over time and only lasts from hours to weeks and hence are not suitable for studying chronicity of the myogenic pain in TMJ disorders. Here we report a model of constant myogenic orofacial pain that lasts for months.
The model involves unilateral ligation of the tendon of the anterior superficial part of the rat masseter muscle (TASM). The ligation of the TASM was achieved with two chromic gut (4.0) ligatures via an intraoral approach. Nocifensive behavior of the rat was assessed by probing the skin site above the TASM with a series of von Frey filaments. The response frequencies were determined and an EF50 value, defined as the von Frey filament force that produces a 50% response frequency, was derived and used as a measure of mechanical sensitivity. Following TASM ligation, the EF50 of the injured side was significantly reduced and maintained throughout the 8-week observation period, suggesting the presence of mechanical hyperalgesia/allodynia. In sham-operated rats, the EF50 of the injured side was transiently reduced for about a week, likely due to injury produced by the surgery. Somatotopically relevant Fos protein expression was indentified in the subnucleus caudalis of the spinal trigeminal sensory complex. In the same region, persistent upregulation of NMDA receptor NR1 phosphorylation and protein expression and increased expression of glial markers glial fibrillary acidic protein (astroglia) and CD11b (microglia) were found. Morphine (0.4-8 mg/kg, s.c.) and duloxetine (0.4-20 mg/kg, i.p.), a selective serotonin-norepinephrine reuptake inhibitor, produced dose-dependent attenuation of hyperalgesia.
Ligation injury of the TASM in rats led to long-lasting and constant mechanical hypersensitivity of myogenic origin. The model will be particularly useful in studying the chronicity of myogenic pain TMJ disorders. The model can also be adapted to other regions of the body for studying pathology of painful tendinopathy seen in sports injury, muscle overuse, and rheumatoid arthritis.
Healthy subjects have a prevalent side on which they display higher-muscle activity during clenching. The relationship between symmetry of masseter muscle (MM) and anterior temporalis (TA) muscle activities and occlusion has been evaluated on the basis of physiological parameters. The aim of the present study was to investigate whether the symmetry of surface EMG (sEMG) activity in asymptomatic young adults is related to symmetry of occlusal contacts. Material. The study population consisted of seventy-two 18-year-old subjects with no temporomandibular disorder (TMD) symptoms. Method. All the participants underwent an sEMG recording with an 8-channel electromyograph (BioEMG III). A T-Scan III evolution 7.01 device was used to analyze the occlusal contact points. Results. The correlation between the activity of right (R) and left (L) TA and the percentage of occlusal contacts was assessed, but no significant differences were found between the RMM and LMM muscles. The differences in the medium values of sEMG between males and females were not statistically significant. Equilibrated muscular activity between RTA and LTA occurred when occlusal contacts reached the percentage of 65% on the left side. Conclusion. The symmetry of sEMG activity in asymptomatic young adults is not related to symmetry of occlusal contacts.
Direct electrical stimulation of the intracranial portion of the trigeminal nerve was performed in 23 subjects undergoing retrogasserian thermocoagulation for the treatment of idiopathic trigeminal neuralgia. In 16 subjects, who were having the operation for the first time, neurological examination was normal, as was neurophysiological testing of trigeminal function. Seven subjects were being operated for the second time, owing to a recurrence of symptoms. In all the subjects being operated for the first time, direct motor responses were obtained from ipsilateral temporalis, masseter and anterior belly of the digastric. The motor conduction velocity was equal for the fibres directed to all three muscles. This was estimated to be 54m/s in the masseteric nerve and 55-68 m/s in the intracranial portion of the trigeminal nerve. Patients who had undergone previous thermocoagulation had a considerably slower conduction velocity. It is supposed that myelin sheaths had been damaged at the first operation.
The masticatory musculature of rodents has evolved to enable both gnawing at the incisors and chewing at the molars. In particular, the masseter muscle is highly specialised, having extended anteriorly to originate from the rostrum. All living rodents have achieved this masseteric expansion in one of three ways, known as the sciuromorph, hystricomorph and myomorph conditions. Here, we used finite element analysis (FEA) to investigate the biomechanical implications of these three morphologies, in a squirrel, guinea pig and rat. In particular, we wished to determine whether each of the three morphologies is better adapted for either gnawing or chewing. Results show that squirrels are more efficient at muscle-bite force transmission during incisor gnawing than guinea pigs, and that guinea pigs are more efficient at molar chewing than squirrels. This matches the known diet of nuts and seeds that squirrels gnaw, and of grasses that guinea pigs grind down with their molars. Surprisingly, results also indicate that rats are more efficient as well as more versatile feeders than both the squirrel and guinea pig. There seems to be no compromise in biting efficiency to accommodate the wider range of foodstuffs and the more general feeding behaviour adopted by rats. Our results show that the morphology of the skull and masticatory muscles have allowed squirrels to specialise as gnawers and guinea pigs as chewers, but that rats are high-performance generalists, which helps explain their overwhelming success as a group.
In this review article different interdisciplinary relevant applications of botulinum toxin type A (BTA) in the head and face region are demonstrated.
Patients with head and face disorders of different etiology often suffer from disorders concerning their musculature (example: synkinesis in mimic muscles) or gland-secretion.
This leads to many problems and reduces their quality of life. The application of BTA can improve movement disorders like blepharospasm, hemifacial spasm, synkinesis following defective healing of the facial nerve, palatal tremor, severe bruxism, oromandibular dystonias hypertrophy of the masseter muscle and disorders of the autonomous nerve system like hypersalivation, hyperlacrimation, pathological sweating and intrinsic rhinitis.
The application of botulinum toxin type A is a helpful and minimally invasive treatment option to improve the quality of life in patients with head and face disorders of different quality and etiology. Side effects are rare.