Introduction[edit | edit source]
James W Lance and Raymond D Adams described this as a rare syndrome characterized by intentional myoclonus as a sequel to hypoxic encephalopathy. Hypoxic encephalopathy can occur due to a cardiopulmonary arrest. LAS can occur in patients who suffer a cardiorespiratory arrest, subsequently regain consciousness, and then developed myoclonus days or weeks after the event. Fewer than 150 cases globally of LAS have been reporated.
- Despite advanced practices in cardiopulmonary resuscitations, the outcomes after cardiopulmonary arrest seem to be poor and people after successful cardiopulmonary resuscitation often remain with some neurological deficits.
- LAS is commonly confused with myoclonic status epilepticus (MSE) even though examination, imaging, level of disability and time of onset are very different 
The acute post-hypoxic myoclonus (PHM) presents within 24 hours of the event is often called myoclonic status epilepticus (MSE), which is one of the predictors for poor prognosis according to the American Academy of NeurologyAcute PHM is considered to be a clinical sign of irreparable brain damage with very less chance of functional recovery in most cases, and when it is accompanied by an absent brainstem reflex and unreactive EEG it becomes a reliable predictor for poor prognosis
The chronic PHM which starts after a few days or weeks in patients who regained consciousness is often stated as LAS, where intentional myoclonus is accompanied when attempting voluntary movements or during a voluntary movement. Dysmetria, dysarthria and ataxia with preserved cognition is also seen in most cases. There have been very few cases reported with acute onset LAS and people diagnosed with LAS has better outcome compared to MSE. The myoclonus in LAS usually subsides with rest or with relaxation. The severity of the myoclonus is very much related to the precision of the movement and it gets exaggerated with startle or emotional stress.
Etiology[edit | edit source]
- Respiratory arrest was found to be the main cause for LAS often followed by anesthesia and surgical accidents
- There are few cases of LAS reported after cardiac arrest, drug intoxication, and asthma attack
Pathophysiology[edit | edit source]
The exact cause for PHM is unclear. Research using human data is lacking in attempts to understand the complex process of PHM. Features of rat models were similar in clinical and pharmacologically to humans with PHM It was proposed that the development of myoclonic jerks after brain hypoxia can be due to the death of Purkinje cells at the fastigial nucleus of the cerebellum which in turn results in loss of GABAergic inhibition and leads to the diaschisis of the motor thalamus and reticular formation of medulla, thereby, increased motor excitability and myoclonus. Abnormalities in the serotonin system also may play a certain role in developing myoclonus
Clinical Features[edit | edit source]
- Generalized, multifocal or focal myoclonus
- Intentional myoclonus sometimes presents with spontaneous myoclonus
- Limb involvement depends on the area of insult whether Cortical or subcortical
- Coma in the acute phase (can also be due to sedation), otherwise awake, alert and cognition relatively preserved
- Dysmetria, dysarthria and ataxia
Neurophysiological Findings[edit | edit source]
- One of the three cases of LAS presents with epileptiform activity
- Spike or poly spike-wave discharges maximally or primarily at the vertex
- EEG was found to be normal in between the myoclonic jerks in some cases
- Giant and normal-sized somatosensory evoked potentials (Freund et al., 2016)
- Demonstrated Jerk-locking was noted in 60% of the cases (Freund et al., 2016)
Medical Management[edit | edit source]
It is very essential to distinguish LAS from MSE so that the right prognosis can be provided, and early management benefits the patient. There are no well-defined treatment guidelines available for LAS. Anti-epileptic drugs such as valproic acid, clonazepam, and/or piracetam/levetiracetam are mostly used.
Bilateral Pallidal deep brain stimulation (Gpi DBS)
(Ritesh et al, 2017) reported the effectiveness of bilateral pallidal deep brain stimulation in post-hypoxic myoclonus, they managed a 23-year-old male with chronic refractory PHM to medication. the study concluded that it is reasonable to use Gpi DBS as a beneficial option in LAS and they suggest Gpi DBS as a viable therapeutic option for PHM.
Physiotherapy Management[edit | edit source]
Even though the pathophysiology of LAS is not been clearly defined, the prognosis is known to be quite good, Physiotherapist should be aware of distinguishing between MSE and LAS. One of the important clinical features is consciousness. In acute PHM patient can persist as unconscious, but in LAS, the patient later regains consciousness
There is a scarcity of literature available in checking the effectiveness of physiotherapy management for LAS. Physiotherapy can play a pivotal role in the management of LAS, focusing on reducing myoclonus severity, improving balance, functional abilities, and postural control and enhancing the overall quality of life. The following are some key approaches in physiotherapy management.
Patient Assessment and Individualized Treatment Plan
- A thorough assessment of the patient's functional abilities, movement patterns, muscle tone, and sensory impairments is essential to develop an individualized treatment plan. Balance and Balance strategies should be assessed well, this allows the physiotherapist to address specific challenges and tailor interventions to the patient's unique needs.
Range of Motion and Stretching Exercises
- Passive and active range of motion exercises, along with stretching techniques, has to be incorporated in managing muscle stiffness, contractures, and spasticity which is often observed in LAS. These help in maintaining joint mobility, reducing pain, and maintaining or enhancing functional movements.
Functional training in repeated and slow motion
- Functional training focuses on facilitating the integration of motor skills into daily activities. It includes task-specific exercises and functional retraining to improve the patient's ability to perform activities of daily living independently
Strength and Balance Training
- Targeted strengthening exercises help improve muscle strength, coordination, and overall stability.
- Balance training including postural control activities and proprioceptive exercise are crucial for enhancing functional mobility and reducing the risk of falls.
Specific Interventions for Balance and Gait training
There are no specific well-defined treatment strategies available for LAS Management. It has been reported that people with ataxia benefit from dynamic task practice challenging the stability, exploring the stability limits and aiming to reduce upper limb weight bearing
- The unexpected waist pull perturbation with A-TPAD (Active Tethered Pelvic Assisted Device)
- Robotic Exoskeleton assisted gait training
Cruz et al in their study concluded that physiotherapy interventions for Myoclonus, postural control, bed mobility and gait training were beneficial for people with LAS. Strategies like deep breathing exercises and approximation were used to control myoclonus. Postural control and weight shifting to promote neuromuscular re-education. For gait training, he used body weight support (BWS), hand-held assistance (HHA), weighted vests and ankle weights were also used.
Role of Multidisciplinary team[edit | edit source]
An early and appropriate pharmacological and rehabilitation regimen promotes a better functional outcome. The multidisciplinary team includes medical, nursing, physiotherapist, occupational therapist, speech therapist, psychologist and social care team
Role of Speech therapist
The speech therapist has an important role in swallowing, speech and cognitive communication. It is found that dyskinesia in LAS creates incoordination in oropharyngeal function. Polypharmacy and sedative properties of benzodiazepine and anticonvulsants also contribute to inattention and incoordination during the oropharyngeal swallow Interventions like speech articulation training, speech-respiration co-ordination and expiratory muscle strength training has found to be effective in LAS
Role of an Occupational therapist
People with LAS may find difficulties during fine motor tasks, as the severity of the myoclonus is very much related to the precision of the movement. Dysmetria and ataxia also make it difficult for them in performing their ADLs. Jorge et al in their case study found it to be effective in treating with 60 minutes of Occupational therapy sessions for 5 days per week, with repetitive task-specific activities for the upper extremities incorporating reaching, ADL, manual dexterity and fine motor skills
References[edit | edit source]
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