A patient head support system comprises a base unit, a head support, and an intervening member for connecting the base unit and the head support. The base unit includes a handle assembly with an elongated body, a bore at one end thereof, and a lever that moves relative to the body between closed and open positions to contract and to expand the bore, respectively. A sleeve retained within the bore is sized to receive and hold a shaft of the intervening member, so as to hold the intervening member in a fixed position when the lever is closed. The sleeve remains retained in the bore when the transition member is disconnected, to resist contracting of the bore caused by inadvertent closing of the lever when the intervening member is unattached, and to protect against the unwanted intrusion of material into the bore.