Lessons From Atypical Groin Pain
Presentation and Treatment of a Schwannoma
Sandra E. Lane, MD; Vijay G. R. Kumar, MD; Lawrence J. Mervis, MD; Dusty Rhodes, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 3 - MARCH 1999
In Brief: A 16-year-old boy presented with pain in the right knee, groin, and hip after a touch football game. He was initially diagnosed as having a medial collateral ligament sprain of the right knee and an adductor muscle strain. Despite standard conservative therapy, he had persistent hip pain and migratory pain to the right lower abdomen and flank. A bone scan and abdominal CT scan were negative, but MRI revealed a mass in the cauda equina at L3-4, confirmed with myelography. A benign schwannoma was surgically excised without neurologic sequelae. The patient resumed daily activities 5 weeks after surgery.
Pain in the knee, thigh, or groin is quite common in physically active young people, and, in most cases, symptoms resolve with conservative measures typically used in treating sprains or strains. However, if symptoms persist despite treatment, as in the case presented below, they may indicate an underlying condition for which the diagnosis requires persistent physical examination and systematic testing.
A 16-year-old male recreational athlete presented in January with pain in his right knee, thigh, and groin. His symptoms had persisted intermittently for several months after a touch football game in which he had twisted his ankle. He recalled no specific trauma to the knee or thigh. He described aching in the groin and stiffness in his knee but no numbness, tingling, swelling, locking, popping, or giving way of the limb. Activities that required abduction of the hip aggravated the groin pain, and he was more symptomatic toward the end of the day. An occasional aspirin and local heat provided minimal relief of his symptoms. His medical and surgical history were unremarkable.
Initial diagnosis and treatment. On physical examination, the patient was comfortable at rest. The medial joint line of the knee was tender on palpation and painful with internal rotation of the knee, but there was no effusion, instability, or weakness of the knee. Flexibility testing revealed bilateral quadriceps, hamstring, and iliotibial band tightness. Right hip and groin pain recurred with external rotation, abduction, and resisted adduction of the hip, but the hip exam was otherwise unremarkable. The neurologic and vascular examinations were normal, and plain radiographs of the knee and hip were negative.
The initial diagnosis was a mild sprain of the medial collateral ligament of the right knee with possible meniscus tear and adductor (groin) and quadriceps strain. The patient was instructed to do stretching exercises and was provided with a knee sleeve to wear for school and work (delivering pizzas). Icing two to three times daily was recommended for the knee and groin. Naproxen (500 mg per day) was prescribed for 10 days, and he was asked to avoid sports activities and return in 2 weeks.
Relief and recurrence. With the treatment described above, the patient was pain free for 5 months. However, his knee and groin discomfort finally recurred during basketball and weight lifting, so he sought medical attention. The results of the follow-up exam were largely the same as those of the previous one, except that the patient had right-side hip pain with resisted hip extension and mild tenderness at the insertion of the right hamstring.
With a working diagnosis of adductor strain and capsulitis of the hip, the patient was advised to avoid sports activities. Treatment included physical therapy with monitored stretching, strengthening, and electrical stimulation and ultrasound for the knee, anterior thigh, and groin. Piroxicam (20 mg, once daily for 10 days) was prescribed to reduce inflammation and pain. A follow-up visit was scheduled in 3 weeks.
The patient returned 5 weeks later. His knee pain had resolved, but the groin and hip pain had increased, especially when he entered and exited his car. Physical exam results were consistent with earlier exams, except that the patient now had tenderness in the right inguinal region. No hernia was detectable. The patient was treated with prednisone (60 mg on the first day and 40 mg on days 2 to 6) to decrease musculoskeletal inflammation in the hip.
Because of the ongoing vague and migratory symptoms involving the groin and hip, a bone scan was obtained to rule out bony pathology of the hip, such as stress fracture or ischemic necrosis. The scan was negative. Consultation with a general surgeon confirmed the absence of an inguinal hernia.
At a follow-up visit, 7 months after initial presentation, the patient noted that his pain, absent while he took prednisone, had returned and was localized to the right lower abdomen and flank. He had no pain along the thoracic or lumbar spine, no change in bowel or bladder habits, and no weight loss.
On examination, the patient had difficulty moving from a seated to a prone position, because of back pain with extension of the lumbar spine. The right lower quadrant of the abdomen was tender, without guarding or rebound. The right flank was tender to palpation, although the lumbar spine was not. The neurologic examination was again negative.
Diagnostic testing. In light of the patient's signs and symptoms, a retroperitoneal mass or lumbar disk pathology was considered. Given his age and the lack of local neurologic abnormalities, an abdominal computed tomography (CT) scan was performed and found to be normal.
Blood chemistries and urinalysis were normal, with the exception of an elevated alanine aminotransferase of 81 U/L (normal, 0 to 35 U/L) and elevated vitamin B12 of 1,567 pg/mL (normal, 200 to 1,000 pg/mL).
Magnetic resonance imaging (MRI) was scheduled to investigate the lumbar spine. It was delayed when the patient, on the recommendation of relatives, began chiropractic treatment. After two visits, his symptoms improved somewhat, and he and his family were skeptical about doing further testing. After we discussed the patient's case at length with them, they relented, and he had the MRI.
The unenhanced MRI revealed an ovoid mass in the spinal canal, dorsal to L3-4, within the cauda equina but not extending into the surrounding bone or through the neural foramen. The mass, which was isodense with cerebrospinal fluid on T2-weighted images and barely visible, was dramatically highlighted on T1-weighted images with gadolinium enhancement (figure 1).
Differential diagnosis. Based on the MRI results, the differential diagnosis included nerve sheath tumor (schwannoma), ependymoma, neuroma, adenoma, meningioma, glioma, sarcoma, and metastatic lymphoma. The tumor, which was well circumscribed and did not appear to be invading surrounding tissues, was thought to be benign.
Surgery. Nearly 8 months after the onset of symptoms, neurosurgical consultation was obtained, and a myelogram was performed, confirming a tumor-like mass at L3-4. At surgery, the tumor was found to be intradural and extramedullary. It surrounded the L-4 nerve root on the right and was dissected from the nerve root fascicle. Intraoperative pathology confirmed the diagnosis of schwannoma. Electrophysiologic monitoring of somatosensory evoked potentials and electromyography were performed during surgery and verified the functional integrity of the nerve root at the end of the procedure.
Outcome. The patient recovered rapidly. He was walking 2 days after the operation, with no complaints of hip, thigh, groin, or knee pain and no neurologic sequelae. He returned home in 5 days, where he limited his activity for 4 weeks until he resumed school.
Two months after the surgery, and nearly a year after the first symptoms appeared, he had fully recovered and eased back into his sports activities without complications. On follow-up 5 years after surgery, he had no neurologic deficit or back or leg pain. A repeat MRI revealed no signs of tumor recurrence.
Schwannomas (neurilemomas) are benign tumors derived from the Schwann cells of the nervous system. They are usually solitary, circumscribed, and encapsulated tumors eccentrically located on proximal nerves or spinal nerve roots (1). Schwannomas are slightly more common in men than women, with peak occurrence between 30 and 60 years of age (2).
Schwannomas tend to grow slowly. Intermittent and progressive symptoms of spinal cord or nerve root compression typically occur over an extended period, with radicular pain reported as the first symptom in about 62% of cases (3). A review (4) of 36 patients who had schwannomas reports a lag time of 6 weeks to 12 years (average, 2.8 years) between the appearance of symptoms and the beginning of treatment. Our patient's 8-month course from presentation to surgery was within that range.
Although some studies using electron microscopy suggest a common stem cell for schwannoma and neurofibroma, the origin of the cells that make up a neurofibroma remains controversial (5). Multiple neurofibromas establish the diagnosis of von Recklinghausen's disease; our patient, however, did not have the stigmata of this disease.
Schwannomas occur with the same frequency as meningiomas, another tumor in the spinal axis, which are usually benign but capable of becoming malignant. They usually develop at the sensory root in a dorsal or dorsolateral location. The majority of lesions are intradural and extramedullary (6), so they can usually be excised without loss of nerve function (2). After complete excision, they rarely recur (in less than 1% of cases) and, for all practical purposes, never become malignant.
The unexpected finding of a cauda equina lesion in such a young man who appeared to have suffered a football-related injury illustrates two important points.
First, if a patient's condition does not improve with conservative treatment, the presumptive diagnosis and treatment must be reexamined: Is the treatment appropriate? Is the patient compliant? Does he or she have a low threshold of pain? Are other factors, such as repetitive stress from work or sports, psychological stress, or underlying medical illness, interfering with normal healing?
Second, if a patient with activity-related symptoms cannot clearly describe the mechanism of injury and if physical findings are inconsistent, the physician must rely on repeated physical examination and a logical, systematic testing process to establish a diagnosis and direct treatment.
Dr Lane is a sports medicine physician, associate medical director, and fellowship director at SportsMedicine Grant, Grant Medical Center, Columbus, Ohio. Dr Kumar is a specialist registrar in neurosurgery at Addenbrookes Hospital in Cambridge, United Kingdom, and is a fellow of the Royal College of Surgeons. Dr Mervis is a neurosurgeon in the division of neurological surgery in the University Hospitals at The Ohio State University in Columbus. Dr Rhodes is a family and sports medicine physician at Miami Valley Hospital in Dayton, Ohio. Address correspondence to Sandra E. Lane, MD, SportsMedicine Grant, 323 E Town St, Columbus, OH 43215.