Bicycle Seat Neuropathy

Background

Bicycle seat neuropathy is one of the more common injuries reported by cyclists (Weiss, 1994). The injuries and symptoms are due to the cyclist supporting his or her body weight on a narrow seat and are believed to be related to either vascular or neurologic injury to the pudendal nerve (Oberpenning, 1994).

Frequency

United States

A wide frequency range has been reported for bicycle seat neuropathy, but it is believed to be underreported. The medical literature contains several case reports of reversible neuropathy (Silbert, 1991; Oberpenning, 1994) and several retrospective studies surveying participants in long-distance cycling races and tours (Kuland, 1978; Weiss, 1985; Andersen, 1997).

Andersen and Bovim surveyed 260 cyclists participating in a long-distance bike tour that was 540 km in length. Of responding males, 22% (35 of 160) reported symptoms of either numbness or pain in the pudendal area. Thirty-three males reported penile numbness, with 10 male cyclists reporting symptoms that lasted longer than one week. Twenty-one males (13%) reported symptoms of impotence, 11 of whom experienced symptoms for longer than one week and 3 of whom reported impotence lasting longer than one month.

Kuland and Brubaker reported that during the 1976 Bikecentennial tour, there was a 7% incidence of pudendal and/or penile numbness, but this study only surveyed 89 out of 1200 participating cyclists.

Weiss studied symptoms of cyclists participating in a 500-mile bicycle tour. Of the participating cyclists, 45% reported at least mild and transient perineal numbness. Ten percent reported the symptoms as severe, and 2% of the cyclists had to temporarily stop riding. Perineal numbness also has been documented in women cyclists. LaSalle et al surveyed 282 female members of a Dallas cycling club. In this group, 34% of the women reported perineal numbness.

Sport Specific Biomechanics

The cause of bicycle seat neuropathy has been attributed to several different ischemic events. Amarenco and Oberpenning hypothesized that compression of the pudendal nerve as it passes through the Alcock canal causes the condition. The Alcock canal is enclosed laterally by the ischial bone and medially by the fascial layer of the obturator internus muscle. The pudendal nerve exits the canal ventrally, below the symphysis pubis, and innervates the genital and perineal regions.

Oberpenning et al postulated that long-distance cycling results in the indirect transmission of pressure onto the perineal nerve within the Alcock canal. Weiss and Bond separately proposed that bicycle seat neuropathy is due to temporary and transient ischemic injury to the dorsal branch of the pudendal nerve secondary to compression of the nerve between the bicycle seat and the symphysis pubis. Weiss also theorized that the genital branch of the genital-femoral nerve could be involved in cases in which scrotal paresthesia is reported.

Bicycle seat design (eg, shape) may be the major extrinsic factor for the development of bicycle seat neuropathy. Results of computer modelling reported by Spears et al in 2003 have shown that wider bicycle seats that support the ischial tuberosities decrease pressure on the perineal area. Other studies have also demonstrated the effect bicycle seat design has on penile blood flow (Jeong, 2002) and penile oxygen pressure (Schwarzer, 2002).

Treatment

Acute Phase

Rehabilitation Program

Recreational Therapy

Recreational therapy should include evaluation of the rider's position on the bicycle and could include changing the seat height and tilt position.

Medical Issues/Complications

Medical issues and complications include continued injury or insult to the area, resulting in continuation of the neuropathy and long-term sequelae such as impotence. Reevaluate the patient after making changes to the bicycle or riding style or after decreasing the training volume to ensure that improvement in symptoms is occurring. Continued symptoms despite changes in the bicycle seat position and training volume may indicate a different source of the symptoms and should warrant reevaluation by the physician.

Consultations

Possible consultants include urology and neurology, based upon the clinical presentation.

Other Treatment

The mainstay of treatment is the adjustment of the bike seat and bike position, such as tilting the nose of the seat down or lowering the seat height to relieve pressure off of the perineum. Other recommendations include having the rider change the style of riding, eg, change positions more frequently or stop riding more frequently.

Newer bicycle seats with a split nose or a center cutout also may help reduce the prevalence of neuropathy by limiting compression on the perineal area . A 2004 study by Lowe et al compared pressure measurements in the perineal area of cyclists on these different bicycle seats and found that some of the newer seats reduced perineal pressure by approximately 50%.

Medication

No medical therapy is recommended.