Full Endoscopic Decompression for a Misdiagnosed Far-Out Syndrome (L5/S1 Extraforaminal Stenosis) in an Elderly Patient with L5 Radiculopathy: Case Report

We present a case of a L5/S1 extraforaminal stenosis (EFS), also known as far-out syndrome, in which ineffective multiple previous fusion surgeries were performed because of misdiagnosis. An 83-year-old man, complaining of back and left sided leg pain along the L5 dermatome for 5 years visited our institute claiming persistent pain even after 2 fusion surgeries at another hospital. A new magnetic resonance image (MRI) scan with a half coronal T1-weighted sequence revealed left L5/S1 EFS and resultant L5 nerve root compression. Because of the patient’s old age, history of angina and anti-platelet medications, a minimally invasive full-endoscopic decompression was performed. Afterwards the patient experienced immediate relief of the radicular pain, satisfied with the surgery. Diagnosis of L5/S1 EFS can be challenging especially when only routine sagittal/axial MRI scans are provided. Half coronal plane T1-weighted image MRI can be extremely helpful in diagnosis of this distinct pathology. Through this case report, we would like to emphasize the significance of half coronal MRI in diagnosis of L5/S1 EFS and also show a representative successful full-endoscopic decompression for the disease.