Deportivo Saprissa remain a point clear after earning a draw at the Estadio Nacional de Costa Rica in San Jose.
In an entertaining and eventful encounter, the league-leading hosts needed a late equaliser from Diego Estrada to avoid giving up top spot.
Kevin Sancho put the visitors ahead on 24 minutes when he headed in the opener before Kenneth Garcia doubled their lead.
Garcia's initial strike five minutes later was saved, but – given a second chance – he finished into the roof of the net.
But in a remarkable turnaround, the hosts were somehow ahead before half-time.
Michael Barquero volleyed in on 39 minutes before David Ramirez headed in the equaliser moments later.
When Barquero scored on the stroke of half-time, Deportivo Saprissa were ahead and took that advantage into the break.
Deportivo Saprissa dominated the early stages of the second half but scores were level on 58 minutes when Alex Robinson headed past his own goalkeeper to make it 3-3.
The hosts squandered chance after chance and were made to pay on 88 minutes when Alejandro Alpizar scored a one-on-one opportunity for Alajuelense.
Deportivo Saprissa got the point they deserved through Estrada, who capitalised on a defensive mistake to level the contest at 4-4.
Third-placed Herediano failed to capitalise on the draw between the top two as they were held to a 1-1 result at UCR.
Perez Zeledon edged Santos de Guapiles 3-2, Puntarenas beat Carmelita 3-2 and Cartagines were 2-0 winners at home to Belen Siglo XXI.
Limon overcame struggling Uruguay 2-1.
