The Five Types of Disc Herniation (that we know of!)
Dystrophic calcification secondary to chondroid degeneration of nucleus pulposus (NP), called a Hanson Type I. This causes mechanical stress on the outer annulus fibrosus (AF), leading to rupture of individual collagenous strands of AF and eventually full failure.
Fibrous degeneration occurs when fibers of disc split leading to accumulation of tissue fluid and plasma between them. Over time the mechanical pressure exerted by NP causes thickening of the AF dorsally, causing protrusion. (Hanson Type II).
ANNPE (Acute noncompressive nucleus pulposus extrusion) - this is normal NP that is exploded into the canal, usually during activity. Also called a traumatic disc herniation.
AHNPE (Acute hydrated nucleus pulposus extrusion) – An apparently normally hydrated NP that is compressive and often located ventral to the cord, often in the neck.
Significantly more neuro deficits and less signs of cervical pain with AHNPE compared to other causes of cervical myelopathy.
FCE (Fibrocartilaginous embolism): a piece of NP that becomes dislodged and finds its way into the vasculature surrounding the spinal cord. This can be into venous or arterial blood vessels. The end result is an acute shift in blood flow at the level of the spinal cord.
Match the clinical sign with the type of disc herniation
A. Chronic, progressive ataxia progressing to paresis
B. Acute, non-progressive unilateral weakness affecting one leg, or one side (hemiparesis)
C. Acute, progressive, painful ataxia progressing to paresis in a chondrodystrophic dog
D. Acute non-progressive ataxia and paresis affecting both sides of the body (paraparesis or tetraparesis)
E. Acute, rapidly progressive tetraparesis and ataxia of all four limbs with minimal cervical pain
If you answered...
Type I: C
Type II: A
ANNPE: D
AHNPE: E
FCE: B
you are correct!
Based on the clinical picture, it can be very difficult to distinguish Type I from ANNPE, and AHNPE. Typically, type I is painful (but not always), and the other two are minimally to non-painful.
Which of these require surgery?
Any disc herniation that results in compression of the spinal cord with associated clinical signs could be considered for surgical correction. This statement would then suggest that Type I, Type II and AHNPE could be surgically corrected. Therefore, any patient with signs of a progressive or painful myelopathy should be evaluated for diagnostic imaging (typically MRI) for possible surgical intervention whenever possible.
Bonus question:
Can you name two diseases that are commonly diagnosed instead of a type I or type II disc herniation? Scroll to the bottom for the answer!
Change is coming! Starting in September I will have new fees, and new availability. I am happy to accommodate outside of these hours whenever possible so please reach out if you cannot find a suitable time using the online scheduler. ( https://barnesveterinaryservices.com/ )
New Hours (Starting September 8th)
Monday 11a-1p, 4-5p
Tuesday 3-4p
Wednesday 11a-1p, 2-4p
Thursday 2-4p
Friday 12-1p
Saturday 9-11a
Bonus Question Answer
Meningoencephalomyelitis (a.k.a meningitis), and neoplasia. Keep these two on your differential diagnoses list when you suspect a disc herniation!!
