====== Idiopathic spinal cord herniation ======

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Rare. The spinal cord herniates through a defect in the dura usually located anteriorly or anterolaterally
between T2–8.

Bone erosion anterior to the dural defect may occasionally be seen 

Frequently associated with a calcified disc fragment, which theoretically may have gradually eroded
through the dura.
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Ventral cord herniation, also known by a variety of other terms such as spontaneous thoracic cord herniation or idiopathic spinal cord herniation, is a rare cause of focal myelopathy due to herniation of the thoracic cord through a dural defect. 

Post surgical cord herniation can occur at any level, usually dorsally in the cervical region following laminectomy.

In the majority of cases no possible antecedent cause is identified and the dural defect is thought to be congenital or idiopathic in nature. In a number of patients a history of previous trauma or surgery in the thoracic region may be present

Clinical presentation is variable, generally with features of a myelopathy. However, progressive Brown-Sequard syndrome is classical, due to herniation of only one side of the cord 
((Watters MR, Stears JC, Osborn AG et-al. Transdural spinal cord herniation: imaging and clinical spectra. AJNR Am J Neuroradiol. 1998;19 (7): 1337-44. AJNR Am J Neuroradiol)).

Idiopathic [[spinal cord herniation]] (ISCH) is an uncommon cause of [[thoracic myelopathy]] in which the [[spinal cord]] herniates or prolapses through an anterior or lateral defect in the [[dura mater]].

This dural defect of unknown origin, is distinguished from herniation with a documented traumatic cause or with postoperative origin. Since the first report of idiopathic spinal cord herniation was published by Wortzman et al in [[1974]]
((Wortzman G, Tasker RR, Rewcastle NB, Richardson JC, Pearson FG. Spontaneous
incarcerated herniation of the spinal cord into a vertebral body: a unique cause 
of paraplegia. Case report. J Neurosurg. 1974 Nov;41(5):631-5. PubMed PMID:
4424434.
)).


===== Idiopathic ventral thoracic spinal cord herniation =====

see [[Idiopathic ventral thoracic spinal cord herniation]].

===== Presentation =====

Commonly presents as an incomplete [[Brown-Séquard syndrome]] (with relative sparing of posterior columns). [[Symptom]]s may be due to distortion of the [[spinal cord]], but [[vascular injury]] may also play a role.

===== Differential diagnosis =====

The main differential diagnosis is with a dorsal [[arachnoid cyst]].

Both result in increased subarachnoid space posterior to the spinal cord, and a ventral kinking of the cord. Contiguous CSF pulsation artifacts on MRI can be seen with cord herniation, whereas an arachnoid cyst tends to interrupt this.

===== Surgery =====

Requires a lateral or anterolateral approach to access the anterior spinal canal while minimizing spinal cord manipulation. The dural defect is widened which usually results in a reduction of the spinal cord herniation. A sling of dural substitute can then be slid anterior to the cord to prevent reherniation.

===== Case reports =====

A 33-year-old female presented with acute [[paraparesis]] after [[spinal anesthesia]] for a [[cesarean section]]. Magnetic resonance imaging (MRI) revealed an intradural mass from the posterior of the T6 to the T8-T9 interface. Parvaresh et al. operated on the patient and after [[laminectomy]] of T6 to T9, the dermoid tumor containing hairs was totally resected and [[cord]] was decompressed entirely. After 6 months, the patient is without any neurological deficit. Puncturing the [[dura]] with cerebrospinal fluid (CSF) in the presence of an extramedullary mass could cause [[spinal cord herniation]] through the blockade. In these cases, awareness about related signs even in the absence of symptoms or complaints could help us to prevent post-SA neurological deficit
((Parvaresh M, Bahrami E, Ahmadi S, Fattahi A, Farid A. Cord Herniation through the Site of Undiagnosed Thoracic Dermoid Tumour during Spinal Anaesthesia; Report of a Case and Describing Ways to Avoid. Prague Med Rep. 2023;124(2):181-188. doi: 10.14712/23362936.2023.15. PMID: 37212137.)).
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An exceedingly rare case of ISCH at the C7-T1 intervertebral disc level in a 44-year-old male presenting with eight months of isolated unilateral sensory symptoms. The diagnosis was made based on the findings on the patient's magnetic resonance imaging of the spinal cord, including the presence of an extradural cerebrospinal fluid collection. Surgical reduction of the herniated segment and patching of the dural defect resulted in a remarkable clinical improvement beginning in the immediate postoperative period. Follow-up MRIs showed no sign of reherniation, and the patient remained asymptomatic after one year of follow-up. Early diagnosis and surgical intervention led to an excellent early outcome in this case. However, long-term follow-up is necessary to monitor for reherniation and relapse of the symptoms in ISCH patients
((Farrokhi MR, Mousavi SR, Rafieossadat R. Idiopathic spinal cord herniation at the cervicothoracic junction level presenting with unilateral sensory symptoms. Clin Neurol Neurosurg. 2023 Jan;224:107526. doi: 10.1016/j.clineuro.2022.107526. Epub 2022 Nov 15. PMID: 36442311.)).