Diencephalic disease

Question 1

What is the diencephalon

Answer 1

The diencephalon is the caudal part of the forebrain and includes:
- the pineal body
- thalamus
- hypothalamus
- sub-thalamus

The hypothalamus extends ventrally as the pituitary which consists of:
- the adenohypophysis (secretes adrenocorticotropin, gonadotropins, thyroid stimulating hormone, prolactin, somatotropins, and other related hormones)
- the neurohypophysis (secretes oxytocin and antidiuretic hormone)

Question 2

How frequent are clinical signs of diencephalic disease in feline practice

Answer 2

Clinical signs of diencephalic disease are uncommon in feline practice

Question 3

What are the clinical signs of diencephalic disease

Answer 3

Problems in this location are heralded by signs associated with endocrinopathy
- polyuria/polydipsia
- insulin-resistant diabetus mellitus
- conformational changes associated with acromegaly or hyperadrenocorticism

Decreased PLRs may be observed if optic chiasm is affected

Question 4

What is the best ancillary exam to confirm a mass lesion in the pituitary gland

Answer 4

Advanced imaging in these cases sometimes identifies a mass lesion in the area of the pituitary gland

Question 5

How frequent are pure thalamic disease in the cat

Answer 5

Pure thalamic disease is rare in the cat

Question 6

What are the clinical signs associated with a pure thalamic disease

Answer 6

Pure thalamic disease may be associated to:
- mild ataxia
- contralateral postural reaction deficits
- contralateral visual deficits
- propulsive circlind
- head deviated towards the side of the lesion
- contralateral hypalgesia
- possible decrease in the level of consciousness and seizures

Question 7

What are the most frequent pituitary disorders

Answer 7

Although rare in the cat, the most frequent pituitary disorders are due to adenomas in either the pars distalis or the pars intermedia

Question 8

What are the clinical signs associated with pituitary tumors

Answer 8

Occasionally pituitary tumors are clinically silent

Often they cause dysfunction related to the endocrinological effects of under or overproduction of pituitary hormones

They can also cause neurological effects due to compression on surrounding structures within the brain from a so-called “macro tumor”
- weakness
- lethargy
- behavioral changes
- blindness
- incoordination

Question 9

What are the signs associated with functional pituitary tumors

Answer 9

Functional pituitary tumors typically cause signs related to excessive adrenocorticotropin (pituitary-dependent hyperadrenocorticism) or growth hormone (acromegaly)

Reduced or absent production of vasopressin (ADH) from the pars nervosa results in central diabetes insipidus which is rare in the cat