#274 brainstem hypoplasia terms

[Melissa Haendel]

There are two seemingly redundant terms, HP_0007362 and HP_0006991, where the latter is a subclass of the former:

Aplasia/Hypoplasia of the brainstem HP_0007362
--Hypoplasia of the brainstem HP_0002365
----Brainstem hypoplasia/dysplasia HP_0006991

'Hypoplasia of the brainstem' definition: Underdevelopment of the brainstem (FMA:79876). [database_cross_reference: HPO:probinson]

No defs for the other two terms.

[Peter N. Robinson]

This is a bundled term that overlapped with the term "Malformation of brainstem structures". It seems that "Brainstem dysplasia" is the closest thing to a standard name for this. I changed the name, and added the definition:
A developmental structural anomaly of the stalk-like part of the brain that comprises the midbrain (aka mesencephalon), the pons (aka pons Varolii), and the medulla oblongata, and connects the cerebral hemispheres with the cervical spinal cord.
I merged the other term with this one, and re-annotated the signle disease associated with it.