Spinal Indentation: Understanding Causes, Imaging Findings, and Outcomes

Spinal indentation, specifically spinal or dorsal spinal cord indentation, is a structural deformation in which the surface of the spinal cord appears pressed or indented on medical imaging. This condition can arise from various factors, such as arachnoid webs, spinal cord herniation, or spinal cysts. Recent advancements in imaging technology, such as MRI, have led to increased identification of these indentations. However, guidelines for managing spinal indentations remain limited, making accurate diagnosis and assessment critical for determining outcomes and treatment options.

What Causes Spinal Indentation?

Spinal indentation can result from multiple structural abnormalities in the spine, with the most common causes including:

1. Dorsal Thoracic Arachnoid Web: This is a thickened layer of arachnoid membrane that presses on the dorsal surface of the spinal cord, causing an indentation. These webs typically form in the upper thoracic region and are usually idiopathic, meaning their cause is not well understood.

2. Spinal Cord Herniation: This condition involves a part of the spinal cord protruding through a dural defect (an opening in the protective membrane around the spinal cord). This can happen due to congenital issues or trauma. Thoracic spinal cord herniation is often found between the T2 and T8 vertebrae and can lead to conditions such as Brown-Séquard syndrome, which causes weakness on one side of the body and sensory loss on the opposite side.

3. Spinal Arachnoid Cysts: These cysts can form within the dural sac or outside it, pressing against the spinal cord and causing indentation. Though often asymptomatic, these cysts can result in neuropathic pain and other symptoms due to the pressure exerted on the spinal cord.

Symptoms of Spinal Indentation

Symptoms of spinal indentation can vary widely depending on the underlying cause and the severity of the indentation. Many cases are asymptomatic and discovered incidentally during imaging for other concerns. However, when symptoms do occur, they often include:

• Neuropathic Pain: A characteristic burning or tingling pain, often radiating along the spine or limbs.

• Myelopathy: This refers to damage to the spinal cord, which can cause weakness, numbness, or coordination issues, especially in the lower limbs.

• Sensory Symptoms: Patients might experience unusual sensations such as numbness, tingling, or a “pins and needles” feeling.

Key Imaging Findings and Their Implications

Advances in imaging techniques have allowed radiologists to recognize subtle spinal indentations more frequently. Key imaging findings associated with spinal indentation include:

• C-shaped Deformity: A characteristic bending or deformity in the spinal cord's shape, often seen in spinal cord herniation.

• Scalpel Sign: A focal indentation resembling the pointed edge of a scalpel, usually associated with arachnoid webs. This sign is visible on sagittal MRI scans and can serve as a clue to the presence of dorsal arachnoid web.

• Cord Diameter Reduction: In some cases, there may be a noticeable decrease in the spinal cord’s diameter due to prolonged indentation.

Outcome and Prognosis for Spinal Indentation

Recent studies suggest that the severity and depth of spinal indentation, as well as associated findings such as syrinx (fluid-filled cavity within the spinal cord), are linked to worse clinical outcomes. Patients with deeper spinal indentations or progressive changes observed during follow-up imaging may face more significant symptoms and, in some cases, may require surgical intervention.

1. Depth of Indentation: Greater indentation depth correlates with a higher risk of developing or worsening neurological symptoms.

2. Presence of Syrinx: Patients with a syrinx formation tend to have a poorer clinical outcome. A syrinx often indicates increased pressure on the spinal cord, exacerbating neurological symptoms.

3. Progression on Imaging: Changes over time in the appearance of spinal indentation suggest an increased risk of clinical deterioration. Follow-up imaging can help assess the progression and guide treatment decisions.

Management and Treatment Options

There are currently no standard treatment guidelines for spinal indentation. Management decisions are usually based on individual assessments of the patient’s symptoms, imaging findings, and risk factors. Common management approaches include:

• Monitoring and Regular Imaging: For patients with mild, asymptomatic indentations, periodic imaging is often recommended to detect any progression.

• Non-Invasive Therapies: Patients with mild symptoms may benefit from a combination of non-invasive therapies, such as chiropractic adjustments, massage therapy, shockwave therapy, decompression therapy, physical therapy, and PRP, to alleviate discomfort and improve spinal function.

• Surgical Intervention: In cases where the indentation leads to progressive symptoms or where there’s a syrinx, surgery may be recommended to relieve the pressure on the spinal cord.

Conclusion

Spinal indentation, or spine indentation, is increasingly detected through advanced imaging techniques, yet its management requires careful consideration. The severity of the indentation, presence of syrinx, and progression over time are crucial factors in assessing the risk of clinical deterioration. As more is learned about the condition, developing standardized guidelines will be essential to provide patients with optimal care based on the latest imaging findings and clinical outcomes.