Benign intraspinal tumour misdiagnosed as mechanical low back pain

Abstract

In December, 2001, a 71-year-old woman was referred to us with low back pain. She had had this pain since 1991, which her general practitioner initially attributed to a mechanical cause. She received conservative treatment and showed improvement, but after 5 years her pain worsened. Several other diagnoses were made, including arthritis, muscle strain, and pain of psychosomatic origin. In December, 2001, she experienced sudden onset of radicular pain around her right knee, associated with numbness and a decreased knee jerk. Neurological examination was otherwise normal and lumbar-spine radiography showed spondylolisthesis. Spinal MRI showed an intradural lesion attached to the L3 root (fi gure). Total resection of the neurofi broma was undertaken, and the patient had complete relief of symptoms on discharge at the end of December, which had been sustained when she was seen for last follow-up in May, 2006. The diagnostic approach to low back pain aims to identify red fl ags that raise suspicion of serious pathology, such as infection or tumour. Since the prevalence of spinal neoplasms in patients with low back pain is 1%, and these tumours present with a long history of non-specifi c symptoms, there is a low index of suspicion among nonspecialists; symptoms can be attributed to mechanical causes and the diagnosis can be delayed, leading to poor outcome. Low back pain is commonly treated in primaryhealth-care settings. The causes of pain are heterogeneous, so specifi c management protocols are diffi cult to formulate. Even though most patients seek initial evaluation by a primary-care physician, they are also managed by rheumatologists, neurologists, orthopaedic surgeons, and neurosurgeons, leading to much variation in assessment and treatment, and to diagnostic delays of less commonly encountered disorders. Because not every patient with low back pain can undergo exhaustive investigation, successful assessment relies on clinical history and examination, aiming to identify red fl ags, such as weight loss, history of cancer, age over 50 years, high ESR, or positive radiological fi ndings. Benign lumbar spinal tumours, however, tend to present without these warning signs. Physicians should therefore look for secondary symptoms that should also raise suspicion of potentially serious disease. Such patients generally present with a long history of increasing pain, not necessarily accompanied by neurological fi ndings, because of a slow growing tumour within the wide lumbar space. Pain can occur at night or when the patient lies down, due to stretching of spinal roots over the mass. Physical examination may show tenderness over the tumour site, stiff ness, abnormal gait, and antalgic scoliosis. These non-specifi c symptoms can be mis interpreted as mechanical or degenerative in nature. Neurological symptoms can present late because of the mobility of lumbar roots. As the tumour grows, it may compress parasympathetic fi bres to the bladder, bowel, or sexual organs, or compromise a single dorsal root. Therefore other diagnoses, including cystocele, prostatic hypertrophy, and atypical sciatica, are also made. Plain radiographs are generally required to ascertain a diagnosis for low back pain. However, the lumbar spine is a diffi cult location for radiological recognition of benign tumours, and plain radiographs can therefore be misleading. CT and MRI are preferable, especially in patients with low back pain and neurological symptoms. Early investigation should not be delayed by atypical features. Benign lumbar spine tumours should not be excluded from the diff erential diagnosis of persistent low back pain. Initial assessment should aim to identify patients at risk of serious causes of low back pain. A high index of suspicion is also required for patients with a confusing clinical presentation, who complain of trivial or atypical symptoms. In such cases, failure of conservative treatment after 3 months, should prompt advanced neurological imaging even if plain radiographs are normal. A high index of suspicion, detailed history and careful physical examination can help identify those high-risk candidates who will need early screening tests.