Hypertonia

Hypertonia is a neurological disorder characterized by an abnormally increased muscle tone, which is frequently seen in conditions related to damage to the central nervous system. It is often used interchangeably with terms like spasticity and rigidity. This phenomenon results from the impaired ability of damaged motor neurons to regulate descending pathways, thereby causing increased muscle spindle excitability and decreased synaptic inhibition. A few scholars argue that the traditional definition of spasticity, being velocity-dependent over-activity of the stretch reflex, might be inadequate as it overlooks patients who display heightened muscle tone without a stretch reflex over-activity. They advocate for the term "reversible hypertonia" as it conveys a treatable condition that can be addressed with various therapeutic interventions, including medication and physical therapy.

Types of hypertonia

Presentation

Symptoms linked to disorders of the central nervous system can be bifurcated into positive and negative categories. Positive symptoms, like rigidity and spasticity, augment muscle activity due to hyper-excitability of the stretch reflex. On the other hand, negative symptoms manifest as insufficient muscle activity, weakness, and diminished motor function. Though traditionally these categories have been perceived as distinct facets of a disorder, some experts believe that they might be closely interrelated.

Injuries and disease of the nervous system (textbook cover)

Pathophysiology

The primary cause of hypertonia is upper motor neuron lesions. Such lesions can be attributed to injuries, diseases, or any condition causing harm to the central nervous system. When the functioning of the upper motor neuron is compromised, it results in a loss of inhibition and a consequent surge in the activity of the lower motor neurons. Depending on the site of the lesion, various patterns of muscle weaknesses or hyperactivity might emerge, leading to symptoms like spasticity, rigidity, or dystonia.

For example:

• Spastic hypertonia is characterized by uncontrolled muscle spasms, shock-like muscle contractions, and abnormal muscle tone. It's common in conditions like cerebral palsy, stroke, and spinal cord injuries.
• Rigidity refers to a severe state of hypertonia where there's resistance during the entire range of joint movement, irrespective of its speed. It's often linked to basal ganglia lesions.
• Dystonic hypertonia is marked by resistance to passive stretching and a tendency to revert to a fixed, involuntary posture post-movement.

Management

Management strategies are best tailored to individual patients. The cornerstone of hypertonia treatment revolves around averting noxious stimuli and ensuring regular range of motion exercises.

Physical Interventions

Physiotherapy has emerged as an effective method to manage hypertonia. Therapies may incorporate stretching exercises to dampen motor neuron excitability, and the overarching goal remains to curb excessive tone, provide the patient a sense of normal positioning and movement, and bolster normal movement patterns. Various techniques such as PNF stretching, inhibitory pressure, and rhythmic rotation are employed. Beyond traditional methods, employing rapid passive movements repetitively to the affected joint has also shown promise. To ensure sustained improvement, regular exercise and patient education are crucial.

Pharmaceutical Interventions

Several pharmacological agents, like Baclofen, Diazepam, and Dantrolene, are predominantly used to treat spastic hypertonia. While Baclofen is preferred for spasticity arising from spinal cord issues, Dantrolene acts directly on muscle tissue. Other drugs like Tizanidine and combinations of Phenytoin with Chlorpromazine might be employed. Ketazolam, though unavailable in certain regions, might further augment the pharmacological repertoire. Administering antispastic medications intrathecally allows for concentrated drug delivery near the action site, which minimizes side effects.

Classification	ICD-10: P94.1 ICD-9-CM: 358 , 779.89 MeSH: D009122 DiseasesDB: 20872

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