I finally talked to Dr. Robin, Harper's geneticist, concerning the CT scan results. He said that it looks like she has enlarged vestibular aqueducts. Here's a snippet I found from nicdc.nih.gov:
Research suggests that most children with enlarged vestibular aqueducts (EVA) will develop some degree of hearing loss. Scientists also are finding that five to 15 percent of children with sensorineural hearing loss, or hearing loss caused by damage to sensory cells inside the cochlea, have EVA. However, scientists do not think that EVA causes hearing loss. Instead, scientists regard EVA as an important clue about hearing loss and its possible causes. This information helps physicians talk with families about how their child's hearing loss may change over time.
The presence of EVA can be a symptom of a genetic disorder called Pendred syndrome, a cause of childhood hearing loss. According to a study by the National Institute on Deafness and Other Communication Disorders (NIDCD), approximately one-third of individuals with EVA and hearing loss have Pendred syndrome. With Pendred syndrome, the hearing loss is progressive, which means that a child will have less hearing over time. Some children may become totally deaf.
In addition to its association with hearing loss, EVA may also be linked with balance symptoms in a small percentage of people. However, the brain is very good at making up for a weak vestibular system, and most children and adults with EVA do not have a problem with their balance or have difficulty doing routine tasks.
This isn't great news but it isn't horrible news either. There are a number of syndromes that have much worse effects than Pendred (i.e. blindness, heart defects, etc.) I am very encouraged that the doctors may finally be heading in the right direction. Dr. Robin is consulting with several other doctors about the test results. He said that the genetic counselor would get back in touch with me soon.