The medulla oblongata or simply medulla is the part of the brainstem. The medulla is continuous with the pons rostrally at the pontomedullary junction and the spinal cord caudally at the C1 vertebrae. Medial medullary structures are the pyramid, medial lemniscus, hypoglossal nucleus, and medial longitudinal fasciculus. Medial medullary structures are supplied by the paramedian branches of the anterior spinal artery, which is a branch of the vertebral artery. The vertebral artery is the subclavian artery branch. The medial medullary syndrome is also known as Dejerine syndrome, which is caused by an infraction of the medial medulla. In 1915, Joseph Jules Dejerine first described this syndrome.
Medial medullary syndrome is most commonly caused by atherothrombotic occlusion of the paramedian branches of the anterior spinal artery, the vertebral artery, or the basilar artery. Common risk factors are dyslipidemia, hypertension, diabetes, and smoking. Other risk factors are atrial fibrillation, atrial septal defect, patent foramen ovale, migraine, and Takayasu arteritis. Dissection of the vertebral artery can also cause medial medullary syndrome, especially among young patients.
Stroke is the world's second-largest cause of death and a major cause of disability. There are almost 800,000 patients in the United States who suffer from an acute stroke every year. Of these strokes, 83 percent are ischemic strokes. 20 to 25% of ischemic strokes occur due to vertebrobasilar artery occlusion (posterior circulation). A variety of neurological syndromes can occur in posterior circulation stroke, medial medullary syndrome is one of them and is a rare cause of ischemic stroke. Approximately 1% of cerebral infarction is due to medial medullary syndrome.
Medial medullary syndrome is caused by a lesion in the medial part of the medulla, which is due to an infraction of vertebral arteries and/or paramedian branches of the anterior spinal artery. So, medial medullary structures, including the lateral corticospinal tract, medial lemniscus, and hypoglossal nerve, are commonly damaged in medial medullary syndrome.
The lateral corticospinal tract controls the voluntary movement of contralateral limbs of the body. The medial lemniscus receives sensory (vibration, fine touch, and proprioception) input from contralateral nucleus cuneatus or nucleus gracilis and sends this signal to the sensory cortex of the brain. Due to the involvement of caudal medulla, hypoglossal nerve (twelfth cranial nerve) damage may occur. The hypoglossal nerve supplies the intrinsic and extrinsic muscles of the tongue except for palatoglossus.
The function of each muscle supplied by the hypoglossal nerve are described below:
Symptoms and Signs
Contralateral paralysis of the upper and lower limb of the body due to lateral corticospinal tract involvement is a common finding. A contralateral decrease in proprioception, vibration, and/or fine touch sensation may occur if medial lemniscus involvement is present in medial medullary syndrome. Some patients report paresthesias or less commonly dysesthesias in the contralateral trunk and lower limb. There are no objective signs of position, touch, or vibration sense loss in many patients with sensory symptoms. In certain patients, a slight loss of position and vibration sense with proprioceptive dysfunction in the contralateral foot is observed.
Ipsilateral deviation of the tongue due to ipsilateral hypoglossal nerve damage (the lower motor type of lesion) can be seen. Although dysphagia is commonly seen in patients with lateral medullary syndrome, it is more common in the bilateral medial medullary infarct. In a review of 28 cases of bilateral medial medullary infarct state, they found 11 cases of dysphagia or palatal palsy.
For evaluation of the patients, it is important to take a relevant clinical history, perform a physical examination, and do appropriate diagnostic tests including:
Risk factors evaluation: Search for risk factors of stroke, including dyslipidemia, hypertension, diabetes, smoking, atrial fibrillation, atrial septal defect, migraine, and Takayasu arteritis.
Neurological examination: A complete neurological examination should be done as medial medullary syndrome is mostly a clinical diagnosis.
Imaging: For the diagnosis of medial medullary syndrome, both computerized tomography (CT) scan and magnetic resonance imaging (MRI) should be done. MRI can visualize the lesion more effectively than a CT scan. It is difficult to visualize posterior cranial fossa structures by CT scan, which may be obscured by the bony structures on CT scan. In diffusion-weighted (DWI) and T2-weighted film, there will be a hyperintense lesion in the medial medulla.
For identifying the site of vascular occlusion, a magnetic resonance (MR) angiogram or CT angiogram can be done.
An ECG can be performed for excluding underlying atrial fibrillation.
Other baseline investigations, including serum glucose, serum electrolytes, fasting lipid panel, etc., should be performed as well.
Management of medial medullary syndrome is similar to any acute ischemic stroke. A rapid evaluation of the patient is necessary for proper management. Management in a stroke center will decrease the mortality and morbidity of these patients.
Intrahospital management steps:
During discharge, the following medications should be considered:
As the brain is permanent tissue, any injury to the brain is not completely reversible. With the advancement of medical science, nowadays, early diagnosis and early initiation of treatment and the use of rehabilitative services, medial medullary syndrome has a fair prognosis. If the patient presents with severe hemiparesis and hemi-sensory loss, then residual hemiparesis and sensory loss may remain for the lifetime. A review of 26 previously reported cases that had bilateral lesions and presented with lingual paresis, quadriplegia, and respiratory symptoms had a bad prognosis.
The most common complications of medial medullary syndrome are deep vein thrombosis (DVT) and pulmonary embolism (PE). Patients may develop severe dysphagia, especially patients with bilateral medial medullary syndrome. Patients can develop aspiration pneumonia. If immediate management is not initiated, then the condition can be fatal. Pulmonary embolism can present with sudden onset dyspnea, which can lead to death. Patients with hemiplegia may develop bedsores. Bedsores can be further complicated by infections and may progress to septicemia and death.
Early rehabilitation is helpful for the patients that have had a stroke. Studies have shown that rehabilitation within 24 hours of the stroke event is not beneficial, compared to the usual stroke unit care. So rehabilitation within 24 hours of the stroke event should be avoided.
Following the stabilization of the patient's condition, secondary preventive measures (patient education, and family education, etc.) should be started to prevent long-term complications. Educate the patient about the risk factors listed below, which should reduce secondary stroke occurrence.
Medial medullary syndrome remains a complex clinical condition that needs communication and coordination between providers at all healthcare levels to bring to bear their specialist skills and collective knowledge for the benefit of the patient. This begins with the initial patient contact by emergency medical service (EMS) to the stroke team's (including clinicians, pharmacists, and nurses) assessment upon hospital arrival. A specially qualified neurologist and neurology specialist nurse will ideally assist in organizing patient treatment, monitoring, and patient awareness, and keeping all team members aware of observations and issues.
The pharmacist will assess possible drug-drug interactions and assist with proper dosage as well as patient care, closely working with clinical personnel if any changes in prescription are needed. Enhanced interprofessional team communication leads to better outcomes in patients with medial medullary syndrome.
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