A lead extension for an electrical stimulation system includes a lead-extension body, terminals, and a connector. The connector includes a contact housing and a gasket housing. Multiple connector contacts are disposed in the contact housing and are coupled to the terminals. A retention member is disposed along one end of the contact housing and is receivable by a retention socket defined in the gasket housing. A deformable gasket is disposed in the retention socket. A lumen extends through the connector and is suitable for receiving an electrical stimulation lead. The received lead is retained in the lumen by using the retention member to compress the gasket along a longitudinal length of the connector. The longitudinal compression of the gasket causes a corresponding radial expansion of the gasket, which retains the electrical stimulation lead within the lumen.
