Discussion:
Thoracic spinal cord herniation is a rarely reported diagnosis in the
literature. The rarity may partly be due to the difficulty in arriving
at the diagnosis due to inconsistent clinical findings[5]. The first
case was reported by wortzman G et al when high resolution MRI was not
available for diagnosis[6]. The study group identified a progressive
Brown-Sequard-like syndrome which was not explained by the usual
etiology[6]. The majority of the spontaneous thoracic cord
herniations reported in the literature are in the form of single case
reports and we found less than 220 cases in the entire literature to
date[1]. Most of the cases of herniations are localised between the
thoracic third and seventh segments in the middle-aged
individuals[7]. The herniation of the spinal cord through the dura
usually occurs through the anterior or anterolateral part of the dural
sheath[1]. The dorsal herniation is very rare[4]. There are few
postulated theories for the herniation of the spinal cord which include
congenital dural deficiency with a preexisting anterior meningocele,
traumatic etiology, duplication of anterior dura, and microscopic
erosion of anterior dura during repeated flexion and extension but none
of these etiologies are proven in literature[1, 2]. So, this
condition is often referred to as an idiopathic condition[2].
The cases of spinal cord herniation show a wide spectrum of symptoms.
The usual presenting symptom is progressive Brown-Sequard type of
syndrome with contralateral altered pain and temperature with
ipsilateral hemiparesis[3]. The neurological deficits may or may not
follow the dermatomal/myotomal distribution. The adhesion of the spinal
cord to the surrounding structures and resultant vascular compromise are
thought to cause neurological deficits[4]. Due to these non-standard
symptoms, many cases of spinal cord herniations were misdiagnosed as
medical causes of paraplegia like multiple sclerosis, demyelinating
neuropathy, and sub-acute combined degeneration of spinal cord[8].
With the wide-spread use of MRI for the diagnosis of spinal conditions,
many cases of spinal cord herniations are being reported in the recent
past. The MRI sagittal view would show focal anterior displacement of
the spinal cord and the axial view shows a lateral defect in the dura
and herniation of the spinal cord[9]. Care must be taken not to miss
the arachnoid cysts if they are present with spinal cord
herniations[9]. The nerve roots are visible in the periphery of the
arachnoid cysts whereas the nerve roots are visible in the dorsal
subarachnoid region in the case of spinal cord herniations without
arachnoid cysts[1, 9].
The usual treatment in patients presenting with neurological deficits
and with a diagnosis of spinal cord herniation is surgical repair of the
herniation[10]. The repair is focused on reducing the cord contents
into the dura and closing the defect. Reducing the cord into the dura
has been shown to improve neurological symptoms[11]. There are few
cases where the symptoms have deteriorated even after surgical
intervention. The cause could be late retethering or the development of
hematoma causing compression. In our case, although the neurological
deficits improved after surgery, there was a sudden deterioration of the
neurology on the third day. This is usually due to hematoma causing
mechanical compression or occlusion of venous drainage. In our case, the
etiology was hematoma and removal of hematoma satisfactorily treated the
symptoms. Ammar et al reported spontaneous retethering in patients with
spinal cord herniation after treatment[12]. The patient should be
kept in constant follow-up and the retethering symptoms should be
explained in detail at discharge.
The evidence available in the literature for treating spontaneous spinal
cord herniations is limited to case reports and few case series. As
there are reports stating spontaneous reduction of the hernia and
deterioration of symptoms after surgery, strong guidelines for the
management of spinal cord herniations are lacking[1]. With the
extensive use of MRI, the number of cases diagnosed as spinal cord
herniation is increasing and strong evidence-based guidelines for which
patients to be treated surgically are the need of the hour.