The term akinesia refers to the inability to perform a clinically perceivable movement. It can present as a delayed response, freezing mid-action, or even total abolition of movement. Akinesia occurs when movement is not perceived either because the amplitude of the movement is small or because the time taken to initiate the reaction is significantly increased. The former is often a consequence of severe bradykinesia, which is commonly mistakenly referred to as akinesia. This makes it difficult to differentiate between the two. In akinesia, there is failure of a rapid build-up of adequate power to initiate the movement.
Akinetic states are associated with numerous etiological causes, that vary with the age of the patient. In adults, akinesia can present alone or as sequelae of neurodegenerative disorders.[1][2] Findings of akinesia noticed antenatally or neonatally is associated with fetal akinesia syndrome.
The causes of akinesia can be classified based on the age group of presentation.
1. Adult-onset akinesia has been associated with the following two causes:
2. The fetal akinetic syndrome (fetal arthrogryposis or Pena–Shokeir syndrome type 1), is a cause of intrauterine fetal death or rarely a live birth, related to diffuse contractures across the body (arthrogryposis) of the fetus and subsequently reduced movement, further leading to intrauterine growth restriction, short umbilical cord, and pulmonary hypoplasia.[3]
It has been found that akinesia in clinically observed parkinsonism is more commonly associated with the motor variant of frontotemporal lobe dementia (FTLD), rather than PD related frontal degeneration. Around 30% of patients with clinically confirmed FTLD showed parkinsonian features, notably, rigidity or akinesia.[4] Acute akinesia is a relatively rare phenomenon and occurs in 0.3% of patients with PD, secondary to infectious pathology or other stressors.[5]
In the pediatric population, akinesia is often associated with the fetal akinetic syndrome. This is associated with high intrauterine mortality. However, the incidence in live births is 1 in 3,000 cases, with over 320 genes implicated in its pathology.[6] It is more predominant in the Asian, European, and African populations.[7]
The pathogenesis of akinesia in adults broadly appears to stem from pallidonigroluysian degeneration that predominantly leads to freezing.[1] However, the specific pathology depends on the type of akinesia. In cases with pure akinesia with gait freezing without any other symptom or diagnosis of PD, it is most likely related to PSP. Evidence of degeneration in the subthalamic nuclei, globus pallidus, and substantia nigra are related to PSP.[8][9]
In patients with PD, the principal cause of akinesia appears to be a dysfunction in phasic and tonic dopamine release. This is in contrast to resting tremors caused mainly due to a dysfunctional tonic phase of dopamine release.[10] Another theory suggests that the akinesia in PD patients is related to bilateral frontal involvement and is also accompanied by deteriorating mental states.[11]
Fetal akinesia has been associated with around 320 genetic variations that could all present with this syndrome. Pathologically speaking, the pathology is evident at all levels, including the brain, spinal cord, motor neuron, neuromuscular junction, and the muscle.[12]
In PD, the examination of a patient with akinesia would reveal freezing mid-movement, festination of both gait and speech, and repetitive upper limb movements.[1] This freezing is typically associated with exaggeration of symptoms with ambulation through narrow spaces like doorways.[13] This usually does not respond to antiparkinson medication.
In akinetic patients secondary to PSP, the rigidity is mainly axial rather than appendicular. The earliest manifestation occurs with recurrent falls, due to profound rigidity, but atypical manifestations like non-specific dizziness, generalized motor slowing, and personality change, could also be present. Slowing of vertical saccades is the most common eye movement manifestation, along with difficulty in down-gazing.[14]
Antenatally, a patient carrying a fetus with possible fetal akinesia can present with reduced fetal movement. Later in the pregnancy, the patient presents with polyhydramnios, evidenced by abnormally increased fundal height.
In a live birth with fetal akinesia syndrome, the following sequence is often observed as a result of a lack of fetal movement.
The determination of akinesia in a patient is mainly clinical and characterized by a delay or inability to react or execute a motor command. Quantitatively, reaction time studies are used to assess the degree of akinesia. It typically reveals a delay in simple reaction time, but a normal choice reaction time.[2]
The neuroimaging studies employed in the assessment of akinesia include:
In patients with akinesia-rigidity dominant PD, in comparison to a tremor-dominant variant, a higher global functional connective density (FCD) in the akinetic-rigid dominant variant is in the left inferior frontal gyrus, right middle frontal gyrus, right superior frontal gyrus along with a lower global FCD in the akinetic-rigid dominant left cerebellum anterior lobule.[15]
Pure akinesia with gait freezing, associated with PSP, has imaging findings showing significant cortical thinning in inferior bilateral frontal, left orbitofrontal, right anterior cingulate, bilateral insula, bilateral supramarginal, right angular and precunial, and bilateral temporal areas, often involving the parahippocampal and lingual gyri.[16] The MRI can show midbrain atrophy with the classic hummingbird sign or the morning glory sign with loss of the lateral convex margin of the tegmentum. Patients have diffuse Tau protein aggregates in the basal ganglia on histopathology.
The current imaging strategies do not give any information on the neurotransmitter type involved in the disorder's pathogenesis. Futuristic models are likely to conduct pharmacological imaging, complex behavioral tasks along with movement analysis techniques, allowing practitioners to quantify the akinesia.[15]
A presumptive diagnosis of fetal akinesia is made after obtaining a normal karyotype and excluding other conditions. Antenatal diagnosis can be carried out as early as 12 weeks of gestation after clinically presenting with reduced fetal movement, fetal edema, or fixed limb posturing, as observed on antenatal ultrasonography.[3]
Treatment of akinesia in adults revolves around controlling the progression of the underlying disease. The management of akinesia is symptomatic rather than curative.
The treatment for fetal akinesia is supportive mainly due to a dismal prognosis in a live birth. Resuscitative measures are initially employed to combat pulmonary hypoplasia. Medications like sildenafil and iloprost to control raised pulmonary pressures are initially used. They can still be converted to a less life-sustaining comfort care approach after adequate discussions with the parents. Antimicrobials may be required. Prolonged parental nutrition is often needed in these patients due to malrotation of gut, short-gut syndrome, and impaired swallowing. Central nervous system anomalies like seizures and endocrine disorders like hypothyroidism need treatment with anticonvulsants and thyroid hormone replacements.[3]
Adult akinesia should be differentiated from:
Live births with fetal akinesia syndrome should be differentiated from:
Adult-onset akinesia has no curative therapy, but symptomatic treatment can significantly alter the damage done to the quality of life in these patients. Although a mild variant of akinesia cannot directly lead to death, severe forms of akinetic crises can cause dysphagia, autonomic dysfunction, and aspiration, which can prove fatal.
Fetal akinesia syndrome has been primarily found to be lethal in utero, with 30% of fetuses being stillborn. The ultimate prognosis is dependent on the underlying cause. The majority of live-born infants usually die within the first month of life. This could warrant an offer for the late termination of pregnancy in countries that allow it.[3]
Fetal akinesia is often lethal within the first month of life. This is due to the many complications associated with this condition.
Akinesia in adults can often present as an emergency, known as akinetic crises. Parkinsonian hyperpyrexia, neuroleptic-like malignant syndrome, acute akinesia, and malignant syndrome in parkinsonism are other terms used to describe these akinetic crises. This variant spectrum may vary from total akinesia with dysphagia, hyperthermia, dysautonomia, the increment of muscle enzymes, and alterations of mental status, to only, the inability or difficulty in initiating movement.[20]
Consultations will be required from neurologist, movement disorder specialist, physical therapy and rehabilitation, and neurosurgeon.
Adult-onset akinesia creates many challenges for both the patient and the family. Since the supportive treatment like physiotherapy and exercise therapy is primarily motivation driven, it is essential to counsel and encourage patients to seek and diligently follow through with it, over a prolonged period. Of importance, is the underlying depressive episode in these patients. Adequate counseling and medication in clinically depressed patients, a condition not uncommon in Parkinson disease and Parkinson plus syndromes, cannot be stressed upon enough.
In parents with a live/stillbirth suggestive of fetal akinesia syndrome, fetal surveillance in subsequent pregnancies is essential. An in utero detection will allow for early termination as an option for the parents. The phenotypic condition is derived from various causes, making the recurrence risk calculation less precise. The stipulated recurrence risk lies anywhere between 0% to 25%.[3] Less life-sustaining comfort care approach after adequate discussions with the parents can be initiated.
An interprofessional team is of utmost importance in providing the best possible outcome both physically and psychologically, for patients with akinesia and their family. While the diagnosis of adult-onset akinesia is dependent on the neurologist, fetal akinesia can be appreciated by an obstetrician and fetal medicine specialist. The rehabilitation of akinesia in adults is heavily dependent on self-motivation and requires regular counseling and psychological evaluation. On the other hand, the parents of a live-born with akinesis, with potentially lethal etiologies, must be counseled and supported when opting for comfort care. Surgeons of numerous disciplines and neonatologists play a role in providing structural and functional corrections in these patients.[3]
The nurse and the pharmacist are responsible for dispensing the right medication and dosage. Finally, physiotherapists' role cannot be undermined in both fetal and adult akinesia as they contribute to significantly improving the quality of life in these patients.
Collaboration shared decision making, and communication is crucial for a good outcome. The interprofessional care must use an integrated care pathway using an evidence-based. The earlier signs and symptoms of a complication are identified, the better is the prognosis and outcome.
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