Tethered Cord Syndrome

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Introduction

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Etiology 

Tethered cord syndrome (TCS) is divided into 2 classifications, which are primary (congenital) and secondary (acquired) TCS.

1.) Primary Tethered Cord Syndrome:

When focusing on primary tethered cord syndrome, the simplest mechanism by which the caudal spinal cord succumbs to tethering is due to a thickened filum terminale. Normally, the filum terminale is a viscoelastic structure that facilitates the ascension of the conus medullaris during neural development . During secondary neurulation, improper canalization of the neural tube allows for precursor cells (most commonly preadipose cells) to proliferate and differentiate, leading to a thickened ‘fatty’ filum terminale  . This thickening prevents the ascension of the conus medullaris, resulting in an abnormally elongated spinal cord. An abnormally thickened filum terminale was classified by Hoffman and colleagues in the 1970’s as being greater than 2 millimetres in diameter .

Lipomas, or fat cell aggregations, around the caudal aspect of the spinal cord have also been linked to TCS. Lipomas associated with TCS are normally subpial in location, whereas subdural lipomas are a lot less associated with this condition (ref 2). The presence of a lipoma can affect both the filum terminale as well as the conus medullaris, essentially leading to an elongated spinal cord and if large enough, may elicit spinal compression as well .

Spinal Dysraphisms, which are any disorders that result in malformations of the spinal cord have also been linked to TCS. Spina bifida occulta, split cord malformations such as diastematomyelia and diplomyelia, and neurenteric cysts, have shown to be connected to TCS .

2.) Secondary Tethered Cord Syndrome: Secondary or acquired tethered cord syndrome can be due to a variety of sources that essentially elicit the fibrotic thickening of the filum terminale, such as: infection, fibrotic scarring and the presence of a tumor (ref 2). Another potential source of secondary TCS could be due to fibrotic thickening following spinal surgery, however, it is said that these individuals most likely possessed abnormal tethering preceding the surgery .

Pathophysiology

Pathophysiology: The aforementioned mechanisms exert their effect on the spinal cord in a few different manners. Yamada et al. demonstrated that after constant or intermittent traction to the spinal cord, oxidative metabolism was decreased overall. It was proposed that this was likely due to the overall ischemic effect of spinal traction, which subsequently leads to hypoxia (REF). Other proposed mechanisms suggest that the disruption of ion channels is also associated with neuronal membrane traction, ultimately contributing to the decreased capacity for oxidative metabolism (REF). Collectively, these mechanisms directly elicit neuronal dysfunction and can progressively worsen overtime. The outcome of these neural dysfunctions are discussed further in the clinical presenation.  (USE THE 3 FOR PATHOLOGY PLUS REF 2)

Clinical Presentation

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Diagnostic Procedures

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Epidemiology

Tethered cord syndrome is usually diagnosed only after the onset of signs and symptoms or found incidentally when looking for unrelated problems. Due to this, the true incidence and prevalence in the general population is not known. However, onset of symptoms seems to appear more commonly in childhood than in adulthood.

Outcome Measures

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Management / Interventions

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Differential Diagnosis

There are many spinal disorders that share similar signs and symptoms as tethered cord syndrome especially in adult onset TCS. These include any condition that results in back and leg pain, motor and sensory deficits or incontinence such as: disc disease, spondylolisthesis, spine diseases, spinal cord disorders, peripheral nerve disease and herniated discs. Yamada and Lonser provide some key characteristics of TCS to look for to help differentiate between some spinal disorders and TCS:
• Motor and Sensory deficits will not follow a normal myotomal/dermatomal pattern.
• Coughing and sneezing will not aggravate the pain.
• Lying supine will not make the pain better.
• Straight leg raising will not aggravate the pain.

Other conditions that could present with similar signs and symptoms include:

Spinal cord tumors: depending on location of the tumor, there could be pain, motor and sensory deficits and in rare cases bladder control could be affected.

Peripheral Neuropathy: Damage to the peripheral nerves can lead to pain, altered sensation and weakness.

Myelopathy: This term describes any neurologic deficit related to the spinal cord and includes a wide variety of spinal conditions including: spinal cord compression, spondylosis and damage due to inflammation or lack of blood supply.

Key Evidence

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Resources

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Case Studies

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