Man in a barrel syndrome (MIBS) is a neurologic syndrome characterized by weakness in the bilateral upper extremities (brachial diplegia) with preserved strength in the face, neck, and bilateral lower extremities.
Clinically a patient appears as though they are "stuck in a barrel" with impaired bilateral arm movement and normal facial, cervical, and lower extremity strength.
MIBS can result from bilateral symmetric injury to the brain affecting motor fibers that control arm movement, and can also occur following injury to the brainstem, cervical spinal cord, bilateral brachial plexus or peripheral nerves.
Systemic hypotension causing bilateral watershed strokes is a common cause of MIBS. Watershed strokes occur between the "border zones" of the cerebral vascular territories. When blood pressure is low to the point that it is insufficient to supply blood flow to the most distal arterial small vessel branches, these "border zones" do not receive enough oxygenated blood to survive, resulting in cell death. Cardiac arrest, causing impaired blood flow to the brain, can cause MIBS.
Man in a barrel syndrome can result from bilateral watershed strokes due to systemic hypotension, such as seen in cardiac arrest.
Man in a barrel syndrome results from damage to the bilateral upper extremity motor fibers, sparing the bilateral lower extremity motor fibers. Bilateral symmetric damage isolated to the upper extremity motor fibers in the motor cortex, corona radiata, internal capsule, basal ganglia, brainstem, anterior spinal cord, cervical nerve roots, brachial plexus, peripheral nerves or neuromuscular junction can result in MIBS. Damage to the anterior horn cells, such as in HTLV-1 or amyotrophic lateralizing sclerosis can also present with bilateral upper extremity weakness.
Evaluation with a detailed history and neurologic examination in which bilateral arm strength is impaired and bilateral cervical, facial, and leg strength is preserved are the first steps in diagnosing man in a barrel syndrome.
Neurologic examination in a patient with MIBS is significant for weakness in the bilateral upper extremities and preserved strength in the bilateral neck and lower extremities.
Once the clinical diagnosis of MIBS is made based on the neurologic exam, the next step is to localize the causative lesion(s).
Once the clinical diagnosis of MIBS is made, the next step is to localize the lesion(s), causing bilateral upper extremity weakness.
Treatment for man in a barrel syndrome varies dependent upon the location and type of neurologic injury.
The differential diagnosis for man in a barrel syndrome includes the following lesions along the neuroaxis:
The prognosis for man in a barrel syndrome depends on the type and location of the lesion(s). The prognosis for recovery from bilateral watershed strokes is variable depending on the extent of ischemic damage. In comatose patients with MIBS following extensive watershed strokes, survival is less than 10%. Bilateral intracerebral hemorrhage tends to have a poor prognosis but depends on the extent of tissue damage. Recovery from cervical spine compressive lesions depends on how quickly the lesion is identified and surgically decompressed. MIBS due to myasthenia gravis can be fully reversible with treatment of myasthenia.
Complications from bilateral intracerebral injury can include cognitive deficits, sensory loss, language dysfunction, weakness, and spasticity. Cervical spinal cord injury complications include weakness, sensory loss, spasticity and bowel, and bladder dysfunction. Bilateral brachial plexus injury complications include motor and sensory deficits in the bilateral upper extremities.
Neurologist consultation to perform a detailed neurologic examination and localize the lesion is the first step in evaluating bilateral arm weakness. Radiologist interpretation of brain and cervical spine imaging to identify the etiology of the causative lesion should be performed. A neurosurgeon may be consulted if the lesion is amenable to surgical intervention, such as a brain tumor or a compressive cervical spinal lesion. Physical therapy, occupational therapy, and physiatry collaborate to design and implement a rehabilitation plan to improve motor function.
Patients with MIBS should be counseled on the underlying etiology of MIBS, whether it may be a stroke, tumor, metastatic, auto-immune or inflammatory disease, and appropriate treatment.
Man in a barrel syndrome is a rare neurologic syndrome involving bilateral upper extremity weakness with preserved neck and lower extremity strength that is important to identify quickly as localization of the lesion(s) causing weakness may be reversible. Bilateral cerebral or cervical spinal lesions are the most common causes of MIBS, although various peripheral neuropathic processes have also been described.
Multidisciplinary coordination is important to identify and treat a person with a man in a barrel syndrome. A detailed history and physical examination by a provider can diagnose MIBS. Radiology technicians and radiologists are integral in identifying the etiology of the underlying causative lesion. Neurosurgery may be necessary for tumors or compressive cervical spine lesions, causing MIBS. Once the underlying lesion is treated, an interprofessional rehabilitation team can help the patient on the road to functional recovery.
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