There are several terms here that look similar but even while related are different:

Brahmadanda
Brahmanadi
Brahmanic cord

Brahmanic cord:
"The spinal medulla with its two nervous cords is the Brahmanic cord." - Samael Aun Weor, The Zodiacal Course


Brahmanadi:
"The Brahmanadi or “canalis centralis” within which the Kundalini ascends exists throughout the length of the spinal medulla... Each one of our seven bodies has its own spinal medulla and its Brahmanadi." - Samael Aun Weor, The Mysteries of the Fire: Kundalini Yoga

"Within the Sushumna Nadi there is a Nadi by name Vajra. Chitra Nadi, a minute canal, which is also called Brahmanadi, is within this Vajra Nadi. Kundalini, when awakened, passes through Chitra Nadi." - Swami Sivananda, Kundalini Yoga


Brahmadanda:
"The vertebral column is known by the Hindus as Brahmadanda or the staff of Brahma. It is also symbolized by the bamboo reed with seven knots that the yogis from India carry." - Samael Aun Weor, Igneous Rose