Pisa syndrome (pleurothotonus) is a rare, acquired movement disorder characterized by an involuntary, sustained contraction of the trunk muscles. It is classified as a form of focal dystonia, involving prolonged muscle contractions that result in twisting movements or abnormal postures. While observed in neurodegenerative diseases, the syndrome is most frequently identified as a specific, drug-induced adverse effect. The muscle activity can be disorienting and painful for the patient.
Defining the Disorder and Its Appearance
The physical manifestation of Pisa syndrome is a sustained lateral flexion, or side-leaning, of the trunk and spine. This distinctive posture gives the condition its name, resembling the famous leaning tower in Italy. Diagnosis is considered when the lateral bending of the trunk exceeds an angle of 10 degrees from the vertical axis while the person is upright.
This involuntary leaning often worsens when standing or walking, reflecting a disruption in the body’s control over posture and balance. The symptoms are mobile, meaning the abnormal posture may lessen or temporarily resolve when the patient lies down. The sustained muscle contraction causing the lateral tilt can lead to significant localized discomfort and pain in the paraspinal muscles.
Primary Pharmacological Triggers
Pisa syndrome is primarily associated with pharmacological agents that impact the brain’s neurotransmitter systems, with antipsychotic medications being the most common cause. Both first-generation (typical) and second-generation (atypical) antipsychotics, used to treat various psychiatric conditions, have been implicated in triggering the syndrome. The risk increases with higher dosages or prolonged use of these agents.
The proposed mechanism underlying drug-induced Pisa syndrome centers on a dysregulation of neurotransmitters within the basal ganglia, the brain structures responsible for motor control. Specifically, it results from an imbalance between the dopaminergic and cholinergic systems. Certain medications may block dopamine receptors, which can disrupt the delicate balance with acetylcholine, leading to the sustained, involuntary muscle contractions seen in dystonia.
Beyond antipsychotics, several other drug classes cause this condition, though less frequently. These include selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants, which affect serotonin and norepinephrine levels. Cholinesterase inhibitors, used to treat dementia, and antiemetics, which block dopamine receptors, have also been identified as less common triggers.
Diagnostic Approach and Differential Considerations
The diagnosis of Pisa syndrome is primarily clinical, relying on a detailed medical history and physical examination rather than specific laboratory tests. Reviewing the patient’s current and recent medication regimen is mandatory. The most telling evidence is the temporal relationship between the onset of the leaning and the introduction or recent change in the dosage of a causative medication.
Clinicians must rule out other conditions that can cause similar postural changes, known as a differential diagnosis. Structural spinal deformities like scoliosis or neurological conditions, such as Parkinsonian syndromes and camptocormia, must be excluded. Unlike scoliosis, which involves a fixed rotation of the vertebrae, Pisa syndrome is characterized by a mobile, lateral flexion of the trunk. The distinction is important because the management approach differs significantly based on whether the cause is a drug or a structural issue.
Management Strategies
The primary management strategy for drug-induced Pisa syndrome involves the cautious and gradual reduction or, if possible, discontinuation of the offending medication. This process must be carefully overseen by a prescribing physician to prevent recurrence of the underlying psychiatric or neurological condition. In many cases, symptoms may improve or fully resolve once the causative drug has been withdrawn or switched to an alternative agent.
For patients whose symptoms persist or when the causative medication cannot be immediately stopped, pharmacological interventions are employed. Anticholinergic agents, such as trihexyphenidyl or benztropine, are frequently used to restore the dopamine-acetylcholine balance and can lead to improvement. Benzodiazepines are another class of medications sometimes used as an adjunctive treatment to help relax the involuntarily contracted muscles.
When the condition is refractory to oral medications, or if the patient cannot tolerate the side effects, Botulinum toxin (BoNT) injections are a targeted option. BoNT is injected directly into the hyperactive, contracted axial muscles, such as the paraspinal or abdominal oblique muscles, which temporarily paralyzes them and helps to straighten the posture. This procedure is often guided by ultrasound or electromyography to ensure precise placement. Supportive measures like physical therapy, which focuses on postural retraining and strengthening, are also a component of the multidisciplinary approach to management.