Management of Cervical Dystonia with Botulinum Neurotoxins and EMG/Ultrasound Guidance PDF

REVIEW Management of cervical dystonia with botulinum neurotoxins and EMG/ultrasound guidance Anna Castagna, MD, and Alberto Albanese, MD Correspondence...

REVIEW Management of cervical dystonia with botulinum neurotoxins and EMG/ultrasound guidance Anna Castagna, MD, and Alberto Albanese, MD Correspondence Dr. Albanese Neurology: Clinical Practice February 2019 vol. 9 no. 1 64-73 doi:10.1212/CPJ.0000000000000568 [email protected] Abstract Purpose of review We provide a practical guide on the use of electromyography (EMG) and ultrasound (US) to assist botulinum neurotoxin (BoNT) treat- ment in patients with cervical dystonia (CD). Recent findings US and EMG guidance improve BoNT treatment in CD. Their use is particularly valuable for targeting deep neck muscles and managing complex cases. There is also evidence that adverse events are reduced when superficial or intermediate layer muscles are injected with assisted guidance. Summary A structured clinical approach, based on functional neck anatomy, guides CD assessment and BoNT treatment. Muscles are selected according to clinical, EMG and US findings. US provides anatomical visualization, while EMG complements by detecting muscle activity. We review here the current practice for assisted treatment of CD through BoNT cycles. We also describe how to recognize and manage the main adverse events. Cervical dystonia (CD) is a challenging condition distinguished by involuntary movements of head, neck and shoulders, often associated with neck pain, that impair daily living activities and reduce quality of life. CD is the most common idiopathic isolated focal dystonia.1,2 Thirty years after the first controlled trial, botulinum neurotoxins (BoNT) are currently considered the treatment of choice for CD: recent practice guidelines reported level A or B recom- mendations for efficacy of different BoNT products in CD.3 A recent meta-analysis reported that BoNT treatment improves CD, including pain, and subjective perception.4 However, many practical questions that remained unanswered by evidence-based studies have been addressed by expert consensus.5,6 CD poses specific challenges compared to other dystonia types: (1) the organization of neck muscles is highly redundant allowing to generate a same head/neck movement through variable combinations of muscle activation7; (2) multiple joints connect the skull base, the cervical vertebrae and the shoulder girdle, allowing complex articulations in different axial planes; (3) pain is a prominent feature, compared to other focal dystonia syndromes, requiring specific attention; (4) oculocephalic and vestibular reflexes are altered by prolonged abnormal head/neck move- ments and perception of head and body positioning is impaired. IRCCS Fondazione Don Carlo Gnocchi (AC), Servizio di Analisi Funzione Locomotoria; Università Cattolica del Sacro Cuore (AA), Istituto di Neurologia; and IRCCS Istituto Clinico Humanitas (AA), Unità Operativa Neurologia, Rozzano, Milano. Funding information and disclosures are provided at the end of the article. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp 64 Copyright © 2018 American Academy of Neurology Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. If BoNT is inappropriately placed, organization of cervical muscles controlling head and neck motility. Compensatory muscles are non-primarily dystonic improvement may be insufficient, muscles that become activated to correct non-natural postures/movements or to realign gaze. Compensatory causing patient dissatisfaction and muscles may be recruited among a variety of neck muscles: as possible discontinuance of treatment. a rule, they should not be injected, because they are sec- ondarily involved. However, activity of compensatory mus- cles may persist following BoNT treatment targeted to dystonic muscles, causing abnormal sensorimotor control and joint position errors that can be retrained by physical Complementary to the traditional approach based on surface treatment adjuvant to BoNT injections.16 anatomy, electromyography (EMG) and ultrasound (US) assistance allow to tailor BoNT treatment to individual needs, to control anatomical and physiologic variables, and to Patient’s perception improve efficacy of treatment.5,6 There is evidence that EMG A support for assessment is provided by the patients. The most and US provide increased accuracy for BoNT injections.8–10 distressing symptoms (whether pain, postures, range of motion They can be usefully combined to detect activity and target limitations, etc.) may be annotated and used to guide the posterior neck muscles.11 decision-making process. Pain is a common reason for seeking treatment in CD and, when related to dystonic muscle over- Muscle selection activity usually improves rapidly after BoNT injections and positively influences the patient’s quality of life.17,18 Pain un- CD patients present remarkably variable combinations of responsive to BoNT can instead be related to compensatory dystonic postures and movements that alter the normal muscle activity, joint distress or disc inflammation. positions of head, neck and shoulders, at rest and during vo- litional tasks. Abnormal movements often combine head turn, tilt, forward or backward shift, flexion or extension, and shoulder elevation.1 Treatment is based on BoNT injections Clinical examination into the muscles deemed responsible for the involuntary Clinical assessment of CD patients includes inspection and movements and postures. For example, in rotational CD palpation (surface anatomy). At the end of appraisal, a list of a classical scheme is based on injecting the ipsilateral splenius candidate muscles actively involved and potentially injectable capitis and the contralateral sternocleidomastoid12 or the ip- is prepared (figure 1). silateral splenius and levator scapulae combined with the contralateral sternocleidomastoid and trapezius.13 It has been Inspection provides a first-line identification of the disor- reckoned that, when a fixed approach based on inspection dered motor pattern and orientates on which muscles are alone is used, 41% of the overactive muscles would be missed potentially involved, particularly by appreciating dystonic and 25% of the inactive muscles would be inappropriately postures (tonic component). A baseline orientation is pro- injected.9,14 The reason is that there is insufficient correlation vided by the caput-collum schema of abnormal postures.19 A between the phenomenology of CD and muscle involvement, “caput” malposition suggests involvement of cervical mus- as a variety of combinations of muscle overactivity can give cles reaching the base of the skull (figure 2) or the atlas, rise to overlapping clinical pictures.15 whereas a “collum” malposition suggests involvement of lower cervical muscles. Frequently there is a combination of both Muscle selection is key for an efficacious treatment. If BoNT types. The different combinations of dystonic movements and is inappropriately placed, improvement may be insufficient, postures can produce variable phenotypes. For the purpose causing patient dissatisfaction and possible discontinuance of of BoNT injections, we practically distinguish: posture pre- treatment. Even when injections are placed into the over- dominant, with few dystonic movements mainly occurring active muscles, however, later changes in the pattern of with volitional head repositioning, tremor predominant, with muscle activation and the development of compensatory a prevalence of head tremor, jerky and postural, with an equal muscle activity often require to readjust the injection scheme combination of postures and movements. and to perform more complex reasoning. Overactive dystonic muscles must be distinguished from compensatory muscles. The anatomical organization of cervical muscles is shown in table 2. In patients with CD, particularly after some years of Dystonic muscles are consistently active in relation to dys- disease course, muscle function may be different from normal tonic movements and postures and are primarily responsible for 2 main reasons: (1) the lever arms may pivot at different for the phenomenology of dystonia. As a consequence of joint angles compared to physiologic action, and (2) voluntary dystonic overactivity, the antagonists may be passively activation may generate an abnormal muscle pattern. For ex- stretched (often causing pain) or may instead actively con- ample, the levator scapulae, that normally lifts the ipsilateral tract, attempting to compensate. Table 1 lists the redundant shoulder, may tilt the head ipsilaterally if the surrounding Neurology.org/CP Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 65 Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited.  Table 1 Basic head and neck movement or postures are Table 1 Basic head and neck movement or postures are generated according to a redundant functional generated according to a redundant functional anatomical organization of cervical muscles anatomical organization of cervical muscles (continued) Action Bilateral activation Action Ipsilateral Contralateral Head extension Rectus capitis major Lateral Semispinali cervicis Rectus capitis minor neck tilt Obliquus capitis superior Levator scapulae Semispinalis capitis Scalenus anterior Longissimus capitis Scalenus medius Splenius capitis Scalenus posterior Sternocleidomastoideus Longus colli Trapezius pars descendens This explains the complexity of identifying muscles responsible of dystonic postures and movements solely based on inspection. Neck extension Semispinalis cervicis Splenius cervicis Levator scapulae musculature fixes the shoulder or may be responsible for Head flexion Sternocleidomastoideus ipsilateral neck rotation.20 EMG recording and US exami- Longus capitis nation allow to recognize changes compared to normal function. Rectus capitis anterior Neck flexion Scalenus anterior The patient must be assessed in different conditions: while Scalenus medius sitting and standing comfortably, with a preferred head po- sitioning at rest, eyes open and closed (to temporarily abolish Scalenus posterior influence of visuospatial integration), while voluntarily Longus colli moving the head back and forth along the 3 axes, and finally using activation and deactivation tasks. Assessment should Action Ipsilateral Contralateral also include standing, walking naturally and using sensory tricks (or gestes antagonistes). Head rotation Obliquus capitis inferior Sternocleidomastoideus Rectus major Semispinalis capitis Neck palpation reveals muscle hypertrophy, evoked pain, and passive range of motion. Muscles located in the superficial Splenius capitis Trapezius (pars descendent) layer can be inspected and palpated; muscles in the in- termediate layers can only be palpated; deep muscles are Longissimus capitis inaccessible to physical examination. A limited range of Longus capitis motion may be due to contractures, contraction of contra- Longus colli lateral muscles, deficient voluntary activation of cervical muscles or joint limitation. These factors may influence the Neck rotation Levator scapulae Semispinalis cervicis potential improvement with BoNT and must be considered Longissimus cervicis Scalenus anterior during the muscle selection procedure. Longus colli Scalenus medius Scalenus posterior Instrumented examination Lateral Splenius capitis head tilt EMG and US examinations complement the physical exam and jointly help identifying which muscles are to be selected Longissimus capitis for injection. Obliquus capitis superior Trapezius (pars descendens) EMG assessment Sternocleidomastoideus EMG recordings can facilitate recognizing the active mus- Rectus capitis lateralis cles, because different muscle combinations may produce a same clinical pattern (table 1). Recordings are performed 66 Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 Neurology.org/CP Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. Figure 1 Algorithm for the practical management of cervical dystonia (CD) Green boxes represent clinical assessment; purple boxes represent muscle selection and targeting. BoNT = botulinum neurotoxin; EMG = electromyography; US = ultrasound. on individual muscles or simultaneously on several muscles with clinical assessment, EMG allows to recognize the primarily (polyEMG). Surface and needle electrodes can be combined to activated muscles, to be distinguished from those that have simultaneously record several superficial, intermediate and a compensatory activation. Selective deactivation of dystonic deep layer muscles before performing treatment. muscles by a sensory trick can also be detected by EMG.22 EMG allows to: (1) test activity of non-superficial muscles, which are inaccessible to physical examination; (2) verify whether US examination muscles display tonic, phasic or tremulous activation at rest or US visualizes the neck region of interest at each cervical level. during specific tasks; (3) assess and compare activity of antag- The US probe must have adequate frequency (between 12 and onistic muscles and detect co-activation,15 lack of activation or 15 MHz) to provide real time visualization of muscles, con- inappropriate activation.21 The patients can be examined during nective fasciae and their surroundings. It is useful to combine specific tasks (e.g., while writing, standing or walking) and US anatomical information with functional and EMG findings during active compensatory or inhibiting maneuvers. Combined before drawing-up a final list of candidate muscles. Neurology.org/CP Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 67 Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited.  Figure 2 Neck muscle illustrations Upper panels: layers of neck sections shown and occipital bone. Middle and lower panels: neck sections redrawn from cadaver at C2, C3, C5 and C7 levels. Three different muscle layers and their attachments are represented by different colors: superficial (yellow), intermediate (light blue) and deep (red). A complete list of neck muscles and their attachments is provided in table 2. LCa = longus capitis; LCe = longus cervicis; LNCa = longissimus capitis; LSC = levator scapulae; MFD = multifidus; OCC = occipitalis; OCI = obliquus capitis inferior; OCS = obliquus capitis superior; RCA = rectus capitis anterior; RCL = rectus capitis lateralis; RCm = rectus capitis minor; RCM = rectus capitis major; RMD = rhomboideus minor; SCAa = scalenus anterior; SCAm = scalenus medius; SCAp = scalenus posterior; SCM = sterno- cleidomastoideus; SPCa = splenius capitis; SPCe = splenius cervicis; SSCa = semispinalis capitis; SSCe = semispinalis cervicis; TRP = trapezius. Measure of muscle size identifies hypertrophy (usually re- unravels anatomical variants. Rhythmic muscle activity syn- lated to dystonic overactivity) or hypotrophy (due to pre- chronous with head tremor can be visualized with US. vious BoNT injections or reduced voluntary activation). US echogenicity may be altered by muscle spasm, repeated Outflow of the solution containing BoNT from needle tip is injections, fibrosis fat or calcifications. US visualizes the also visible under US guidance, and its diffusion within the muscle surroundings, particularly arteries, veins and nerves, targeted muscles can easily be appreciated (figure 3). and helps planning a suitable trajectory for injection. Without US, a thin muscle could easily be trespassed or missed. Fur- thermore, US allows to measure the depth of deep muscles from BoNT injection skin surface and consider the width of subcutaneous tissue Injections follow muscle selection. Usually few muscles are (particularly in fat subjects) to calculate the target position. US injected at initial treatment cycles, and more extensive visualizes muscle contraction during selected movements and treatment schemes are later implemented, if needed. 68 Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 Neurology.org/CP Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. Table 2 Anatomical organization of cervical muscles Muscles Upper attachment Lower attachment Superficial layer (yellow in figure 2) Platysma Masseter skin area Thoracic skin area* Sternocleidomastoideus Processus mastoideus and OB (linea nuchalis superior) Suprasternal notch and clavicula (medial part)* Trapezius (pars descendens) OB (linea nuchalis superior)* Clavicula (lateral part) Intermediate layer (blue in figure 2) Rhomboideus minor C7s–T1s* Scapula (medial border) Scalenus anterior C3t–C6t* First rib Scalenus medius C2t–C7t* First rib Scalenus posterior C4t–C7t* Second rib Levator scapulae C1t–C4t* Scapula (superior angle) Splenius capitis Processus mastoideus and OB (linea nuchalis superior) C7s–T3s* Splenius cervicis C1t–C3t T3s–T5s* Deep layer (red in figure 2) Longus capitis OB (basilar part) C3t–C6t* Longus cervicis Atlas (anterior tubercle) C2t–C5t* Rectus capitis anterior OB (basilar part) C1t* Rectus capitis lateralis OB (basilar part) C1t* Obliquus capitis inferior C1t C2s* Obliquus capitis superior OB (linea nuchalis inferior) C1t* Rectus capitis minor OB (linea nuchalis inferior) C1s* Rectus capitis major OB (linea nuchalis inferior) C2s* Longissimus capitis Processus mastoideus C3t–T4t* Multifidus From C4 to L5 t* Inserts above every 2–4 vertebras Semispinalis cervicis C2s–C5s T1–T6t* Semispinalis capitis OB (linea nuchalis superior) C7s–T6s* Abbreviations: OB = occipital bone; s = processus spinosus; t = processus transversus. Three muscle layers are identified by colors in figure 2: superficial layer (yellow); Intermediate layer (blue); deep layer (red). For each muscle the origin (asterisk) and the insertion are indicated. The needle tip should reach the muscle belly or be in proximity of without guidance in the sternocleidomastoid muscle, provided the endplate zone.23 Multiple injections per muscle provide a specific eliciting maneuver is performed (figure 4); however, better results than single-point injections.24 The number of in- should side effects occur, US guidance is recommended.10 For jection points has to be increased in longer multi-segmental all other cervical muscles precise targeting requires at least one muscles, such as the semispinalis capitis or in muscles with more instrumented guide, either EMG or US. A portable EMG de- than one belly, like the levator scapulae or the sternocleidomas- vice providing acoustic feedback is sufficient to detect muscle toid. The trapezius can be injected into different portions (pars overactivity and assist in targeting. This is particularly useful for descendens, pars trasversalis), depending on which abnormal delivering treatment outside a fully equipped BoNT clinic. posture or movement of head or shoulder need to be corrected. Devices combining US and EMG capabilities are also available. Currently, there are no recommendations on when to use either US guidance allows to visualize the needle while performing EMG or US or both, and on which patients. The use of guided the injection (figure 3) and to devise trajectories for injecting injections currently depends on the experience and comfort multiple muscles at different depths along a single track, level of the individual injector. BoNT injections can be made reducing pain and discomfort to patients. For example, it is Neurology.org/CP Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 69 Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited.  Figure 3 Muscle ultrasound (US) US image at C2 level showing the injecting needle with outflow of BoNT solution from needle tip into the spe- nius capitis muscle (arrow). Superficial, intermediate and deep layers are shown. Distances from surface are reported on the right with 0.5 cm marks, from 0 to 5 cm. Figure 4 Procedure for a safe approach to injection of the sternocleidomastoid muscle guided by inspection The head is turned contralaterally by approximately 30°, then the chin is gently pushed down (1); the SCM is pinched with 2 fingers (2) and injected from below tangentially to muscle fibers in the upper third of the muscle belly (3). This approach minimizes BoNT dif- fusion to the swallowing area and does not necessarily require ultrasound (US) guidance. 70 Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 Neurology.org/CP Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. possible to inject sub-occipital muscles at C2 level, by inserting There are no controlled trials a needle nearly 30° posteriorly from the midline: the trapezius pars descendens, the splenius capitis, the semispinalis capitis addressing treatment strategies and the obliquus capitis inferior can be reached along a single track (figure 3). Furthermore, at C3 level, nearly 70° from when repeated BoNT injection cycles the posterior midline, with a single penetration the following are performed. muscles can be injected: splenius cervicis, levator scapulae, longissimus capitis and multifidus. Finally, a needle inserted at C7 level, nearly 45° from midline, may sequentially reach the trapezius, the levator scapulae and the scalenus posterior along the same trajectory (figure 2). dilution are performed according to the approved label. More concentrated dilutions may prevent or reduce unwanted dif- There are 2 main groups of deep neck muscles requiring fusion to nearby sites, such as swallowing muscles.29 Typical expert management: posteriorly, the sub-occipital muscles, dilutions with normal saline solution for CD are: 0.5–2 mL for located deep to the semispinalis capitis in proximity of the 100 onabotulinumtoxinA or incobotulinumtoxinA U, 1–2 mL great occipital nerve, and anteriorly the deep flexor muscles, for 500 abobotulinumtoxinA U. Liquid rimabotulinumtoxinB in proximity of the trachea and vertebrae. can be injected at the pre-set dilution of 5,000 U/ml. There are 4 sub-occipital muscles: rectus capitis posterior ma- jor, rectus capitis posterior minor, obliquus capitis superior, and Assessment of outcome obliquus capitis inferior. The first 3 extend the head on C1-C2; Particularly after the first treatment cycle, but also at later cycles, the rectus capitis major also contributes to the ipsilateral rota- it is important to rate outcome at time of peak effect (between 4 tion of the head and the obliquus capitis superior additionally and 6 weeks after BoNT treatment) using validated rating scales. tilts the head on a side. The almost horizontal obliquus capitis Two scales were recommended by the International Parkinson inferior is inserted on the transverse process of the atlas and and Movement Disorder Society: the CD Impact Scale-58 and originates from the spinous process of epistropheus. This thick the Toronto Western Spasmodic Torticollis Rating Scale.30 The muscle rotates the atlanto-axial joint for a narrow angle (nearly same task force also suggested 3 other scales for use in CD: 10°): it is a strong head rotator and contributes to head the Tsui scale, the Functional Disability Questionnaire and the movement related to fast visual exploration. Body Concept Scale. Outcome at time of maximal expected efficacy should be compared to the before treatment condition. There are 3 anterior flexor muscles: longus capitis, longus Videotape recordings are a useful tool for objectively document colli (or cervicis), and rectus capitis anterior, which exert the patient status; video footage should be structured according a rotatory action if activated unilaterally. The anterior flexor to a uniform set of sequences, for example following the dys- muscles contribute to the “double chin” posture25; particu- tonia study group videotape protocol.31 larly the longus colli may cause loss of physiologic cervical lordosis. Synergically with them, the rectus capitis lateralis contributes to lateral head tilt. The longus capitis and longus colli can be injected at C5 level with EMG and US guidance Follow-up treatments by experienced injectors.26 When hypertrophic, they can CD is a chronic disease with clinical variability over its course. It alternatively be targeted with a trans-nasal or trans-oral has been reckoned that the complexity pattern remains stable in technique using endoscopic inspection.27 approximately 64% of CD patients under BoNT treatment, while complexity increases or decreases in the remaining 36%.32 For head tremor bilateral injections are usually performed in BoNT treatment consists of repeated cycles, with intervals muscles that are active synchronously to tremor. For “no-no” lasting for approximately 12 weeks. Recent evidence suggests head tremor injections are typically placed bilaterally in the that CD patients may be better treated using individually ad- splenius capitis or in the obliquus capitis inferior, depending justed intervals,33 keeping a minimum distance between cycles, on EMG recordings.11,28 There is limited knowledge re- as indicated on product labels. garding “yes-yes” or “round-and-round” head tremors. In the first type, the sternocleidomastoid or the anterior scalene can Follow-up treatment sessions are influenced by earlier treat- be targeted; in some head tremors, the levator scapulae and ment cycles and their outcome. An effective treatment strategy the longissimus capitis can be additionally injected. If there is is based on 2 premises: (1) a successful outcome supports a clearly recognizable directional preponderance, as in jerky repeating the same treatment scheme, (2) refinements are often head tremors, muscle selection will take into first account the needed at later cycles. Occasionally, a previous muscle selection prevalent direction of pull. strategy needs careful re-planning, particularly when outcome is unsatisfactory, phenomenology changes or pain is prominent. There is no study directly comparing the efficacy and tolera- There are no controlled trials addressing treatment strategies bility of different BoNT dilutions in CD. Reconstitution and when repeated BoNT injection cycles are performed. We Neurology.org/CP Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 71 Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited.  consider that approximately 3 consecutive treatment ses- potentially lead to an increase of side effects due to proximity of sions are necessary before a treatment plan stabilizes. Mus- surrounding deep neck structures (such as roots or arteries). cles that become hypotrophic are re-injected with lower EMG- and US-guided injections have impact on visit time and doses under US guide (rather than being left without treat- costs. Payers do not normally question EMG or US for BoNT, ment), unless it is considered that they are inactive. although there are currently no clear payer policies on the use of guided injections.38 The efficacy and safety profiles of BoNT Muscle selection and dosage at follow-up cycles is driven by in patients with CD have a direct influence on medical deci- the same decision-making process. Deep layer muscles are sions, particularly because surgical treatments, such as deep usually added during follow-up assessment, particularly if brain stimulation, provide an alternative option. BoNT failure, they were not considered at earlier sessions. Thus, the defined as a less than 30% symptom improvement, has been treatment strategy through cycles can be generally regarded considered an indication for surgery.39 The use of EMG and US as moving from more superficial to deeper muscle layers. assistance may improve outcome in patients otherwise poorly Deeper muscles may also become more active once superfi- responsive to BoNT treatment, who could be addressed to cial muscles are inactivated by BoNT. alternative treatment options. Author contributions Management of adverse events A. Castagna: drafting/revising the manuscript, data acqui- BoNT injections into neck muscles are usually well tolerated. sition, analysis or interpretation of data. A. Albanese: According to a recent meta-analysis, BoNT treatment of CD drafting/revising the manuscript, data acquisition, study is associated with an increased risk of 2 adverse events: concept or design, analysis or interpretation of data, study dysphagia and diffuse weakness/tiredness.4 Other adverse supervision. events, reported with similar prevalence in placebo-treated patients, include: neck weakness, voice changes/hoarseness, Study funding sore throat/dry mouth, vertigo/dizziness, malaise/upper No targeted funding reported. respiratory infection, injection site pain and headache. These events are transient, and usually mild or moderate, not re- Disclosure quiring specific management. Dysphagia and neck weakness, A. Castagna has received speaker honoraria from Ipsen and instead, need special attention, particularly if severe, as they Merz. A. Albanese serves on a scientific advisory board for are potentially harmful. Weston Brain Institute; has received speaker honoraria from Allergan, Merz, and Ipsen; and serves as Associate Editor for Dysphagia, caused by spread of BoNT to pharyngeal muscles, is European Journal of Neurology and Specialty Chief Editor for a redoubtable side effect particularly if injections are placed in Frontiers in Neurology. Full disclosure form information anterior muscles. It occurs from 1 to 10 days after BoNT in- provided by the authors is available with the full text of this jection and lasts on average 15.8 days.34 Iatrogenic dysphagia article at Neurology.org/cp. has to be distinguished from dysphagia associated with CD that Publication history is observed independently of BoNT treatment.35 Experience Received by Neurology: Clinical Practice May 29, 2018. Accepted in final collected in the pioneering BoNT age indicated that bilateral form August 28, 2018. injections in the sternocleidomastoid muscles are frequently associated with dysphagia.36 From these observations it became References practice to inject in the upper portion of the sternocleido- 1. Jankovic J, Leder S, Warner D, Schwartz K. Cervical dystonia: clinical findings and associated movement disorders. Neurology 1991;41:1088–1091. mastoid muscle (figure 4). Alternatively US guidance can be 2. Albanese A, Bhatia K, Bressman SB, et al. Phenomenology and classification of dys- used to reduce the risk of dysphagia.10 In a recent meta-analysis, 3. tonia: a consensus update. Mov Disord 2013;28:863–873. Simpson DM, Hallett M, Ashman EJ, et al. 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Borodic GE, Pearce LB, Smith K, Joseph M. Botulinum a toxin for spasmodic torti- medication-refractory cervical dystonia: a randomised, sham-controlled trial. Lancet collis: multiple vs single injection points per muscle. Head Neck 1992;14:33–37. Neurol 2014;13:875–884. Practical Implications Neurology® Clinical Practice is committed to providing clinical insights helpful to neurologists in everyday practice. Each Full Case includes a “Practical Implications” statement, a pearl of wisdom for the practicing clinician. Neurology.org/CP Neurology: Clinical Practice | Volume 9, Number 1 | February 2019 73 Copyright ª 2018 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. View publication stats