... do you think we are discovering that the malformation in the cavalier skull causes this PSOM issue as well? ...
In a July 2010 study report, UK researchers found an association between PSOM and brachycephalic conformation in cavaliers. In their report, they find, "in CKCS, greater thickness of the soft palate and reduced nasopharyngeal aperture are significantly associated with OME [otitis media with effusion, meaning PSOM]."
But, PSOM is common only in the cavalier. It has been found in three other breeds, like 9 boxers, one dachshund, and one shih tzu. So, it is not a widespread brachycephalic problem. But it could be related to the cause of Chiari-like malformation because so many cavaliers are found to have both CM/SM and PSOM. Then, again, nearly all cavaliers have CM and most have SM, so that combination may not mean much.
I don't know about other breeds, but here is a list of genetic disorders that either are unique to the CKCS or are much more common in the CKCS than most other breeds:
Mitral valve disease
Chiari-like malformation and syringomyelia
Idiopathic asymptomatic thrombocytopenia (low counts of blood platelets)
Macrothrombocytosis (oversized blood platelets)
Cerebellar infarcts (strokes)
Dry eye
Curly-coat syndrome
Abiotrophic sensorineural deafness
Eosinophilic stomatitis
Episodic falling syndrome
PSOM
Masticatory muscle myositis
Chronic pancreatitis