DISCUSSION
Intradural disc herniation (IDH) is a rare phenomenon , which accounts
for only 0.25 to 0.35 %[2] of all disc herniations with lumbar
region being the most common site of occurrence[3]. The level most
frequently affected is L4-L5 [4]. Male are more likely to have the
disease entity than female. Average age of onset is between 50 -60 yrs.
Symtoms of IDH may vary depending upon location of disc herniation, with
cervical IDH patients presenting with clinical findings of Brown Sequard
Syndrome [5], [6], or incomplete and trainsient quadriparesis
and those involving lumbar region presenting as long history of
radiculopathic pain with acute presentation consisting of symptoms of
cauda equina syndrome [4]. In our patient both radiculopathy and
cauda equina symptoms improved gradually post operatively with poor
improvement of bladder function for which physiotherapy and acupuncture
therapy was provided to patient.
The pathogenesis of IDH remains unclear, however few theories have been
proposed. Several reports suggested that certain factors like reduced
epidural space resulting from congenital or iatrogenic narrowing of
spinal canal, adhesions between annulus fibrosus, posterior longitudinal
ligament (PLL) and ventral dura matter were responsible for IDH [7],
[8]. Among the aformentiond pathogenesis adhesion between PLL and
ventral dura matter was considered to be an important factor [9],
[10]. Tateiwa [11] stated that factors such as local trauma,
previous spine surgery or even congenital factors like dural thickness
were responsible for adhesions. Floeth and Herdmann
[12] reported that chronic inflammation, as a result of degenerative
disc pathologies, favors development of adhesions and lead to erosion
process with thinning of the dura. Dura matter and PLL are in closest
proximity at L4-L5 level which explains the highest incidence of IDH at
L4-L5 level [13]. In our case, there was dense adhesion between PLL
and ventral dura and we speculate that previous history of trauma with
disc degeneration resulted into chronic inflammation , and during this
process long term irritation, inflammation with a sudden force caused
the prolapsed disc into the intradural space through the dural erosion.
A preoperative assumption and diagnosis of IDH is difficult. Lesions
might be ignored or can easily be mistaken for other findings on
imaging. Definite diagnosis are made only on surgery, not via imaging
alone. The MRI in our case did not indicate the presence of intradural
disc fragments and definitive diagnosis was made
intraoperatively.