Neurosurgery notes/Spine/Spinal Degenerative Diseases/Thoracic disc

Thoracic disc

View Details
Status
Done
logo
Parent item
Spinal Degenerative Diseases

Introduction

  • The kyphosis of the thoracic spine is offset by the lordosis in the mobile cervical spine and the principal load bearing lumbar spine maintaining a sagittal balanced posture.
  • The thoracic spine and its articulation with the rib cage maximizes the stability of the thoracic spine while minimizing its mobility leading to the low incidence of thoracic disc prolapse.

Numbers

  • Incidence
    • 1 per 1 000 000 patient years (McInerney and Ball, 2000).
    • Incidental thoracic disc herniations 11% (Awwad et al., 1991).
  • Consist of
    • 0.2% - 4% of all symptomatic protrusions of an intervertebral disc
    • 0.2% to 1.8% of all operations performed on symptomatic herniated discs.
  • 1:1 male to female ratio
  • 30s-60s
    • Similar to cervical and lumbar disc herniations (McInerney and Ball, 2000)
  • Common level
    • Most below T7 (75%)
      • Due to the structural stability provided by the upper thoracic cage
      • most common level T11/ T12
        • Due to hyper mobility
  • Massive disc
    • If >40% of canal
    • Mainly calcified
    • High risk of intradural extension: 15%
  • Majority are central or centrolateral.
  • Aetiology
    • 75% Degeneration
    • 25% trauma.
      • Usually occur in the younger age group.
  • 30– 70% of discs are reported to be calcified with a high incidence of calcified discs being intradural.

Classification

notion image
notion image
notion image

Clinical features

  • Pain (92%)
    • The majority of the literature demonstrates that pain is the predominate symptom at presentation.
    • Axial back pain
    • Upper thoracic
      • radicular pain radiating around the anterior chest wall
    • Lower thoracic
      • Abdominal pain
      • Lumbar pain
    • 25% of patients present without pain, complaining of a subtle neurological deficit or gait disturbance which can contribute to a delayed diagnosis.
    • Pain can be unilateral or bilateral and the region it radiates to depends on the level.
      • Temporal
        • In disc herniations due to degeneration
          • Pain (thoracolumbar or radicular pain) --> sensory disturbance --> motor dysfunction --> bladder and bowel dysfunction (Arce and Dohrmann, 1985).
        • In traumatic disc protrusions
          • Pain --> myelopathy (Arseni and Nash, 1960).
  • Myelopathy
    • Sensory disturbance
      • Sensory changes for pin prick the first signs
    • Spastic paraparesis
    • Muscle weakness
      • T1/ T2 discs can present with upper limb radiculopathy with pain radiating down the upper limb and weakness of the intrinsic muscles of the hand.
    • bladder or bowel dysfunction
  • Horner syndrome
    • For upper thoracic disc herniation
  • There is significant variation in the presenting symptoms and signs of thoracic disc herniation from case to case.
    • Due to
      • Spinal level
      • Position
      • Size of the herniated disc
      • Bony canal
      • Duration of compression
      • Degree of neurovascular compromise
      • Aetiology

Pathogenesis

  • Neurological signs and symptoms are due to direct neural compression and vascular insufficiency.
  • Compression at the levels T4- T9 can have a significant impact of the spinal cord due to the vulnerable blood supply at this level.
  • Thoracic spine vulnerability
    • Thoracic Kyphosis
      • Spinal Cord/Dural Sheath flattened against posterior portion of disc
    • Diameter of the Spinal Cord
      • Large relative to the thoracic spinal canal
    • Watershed Zone
      • Blood supply between T4-9
    • Intradural Extension
    • Denticulate Ligaments
      • Limit spinal cord mobility within the dural sheath

Natural hx

  • There is little published information regarding the natural history of asymptomatic thoracic disc protrusion.
  • Wood et al., 1995and 1997
    • Incidence of asymptomatic thoracic disc protrusion ranges from 15% - 37%
    • 90 asymptomatic thoracic disc, over a mean of 26 months
      • herniated discs remained asymptomatic but small discs tended to remain unchanged or increase in size, whereas large discs tended to decrease in size (Wood et al., 1997).

Investigation

  • Whole spine MRI
    • Cord compression:
      • Myelomalacia
      • Cord oedema
    • Ligamentum flavum buckling
    • DWI
      • Cord infarction
  • CT scan
    • determine if calcification is present in the prolapsed disc.
    • 42% are calcified

DDx

  • Spinal stenosis
  • Neurology
    • ALS/MS
  • Neoplastic: Meningioma osteoid osteoma
  • Vascular AVM CVA
  • Infectious disc vs body
  • Ankylosing spondylitis
  • Fracture

Management

  • Conservative
    • Indicated for
      • No long-tract signs or myelopathy
    • Options
      • Trial NSAlDs
      • Gradual mobilization - limit: axial loading and repetitive flexion/extension/twisting
      • Bracing with TLSO may help
      • PT for postural training, extension strengthening, and CV conditioning
Surgical (See thoracic approaches)
  • Indication
    • Myelopathy
      • Progressive neurology
        • myelopathy
        • bladder or bowel disturbance
        • Any long- tract signs.
      • Pain refractory to medical management
    • Radiculopathy
      • once the level is confirmed using a nerve root block, can be treated via a less extensive surgery for exiting nerve root decompression.
Level Localization
  • Radiological Marking cement — coil
  • Always count from sacrum
  • Surgical timing: Day time surgery
  • Surgical options
      • Depends (Arts and Bartels, 2014)
      • Level of the disc prolapse
      • Position of the disc in relation to the neural structures
        • Lateral lesions:
          • Transpedicular
          • Lateral extra cavitary
          • Costotransversectomy
        • Central lesions: transthoracic (anterior/ventral)
          • High thoracic - Right (avoid great vessels)
          • Mid thoracic - Left (avoid heart)
          • Low thoracic - Right (easier to mobilize aorta)
      • Consistency of the disc (soft vs. calcified)
        • Calcified
          • Anterior
        • Soft
          • Lateral
      • Whether or not the disc is intradural
      notion image
       
      notion image
      Anterior
      • Indication
        • Calcified
        • Central disc
      • Options
        • Transthoracic
            • Trans pleural, Extra pleural, Transsternal
            • Right-sided thoracotomy preferred for midthoracic because heart does impede access
            • Left-sided preferred for lower thoracic (easier to mobilize aorta than vena cava)
             
            Central disc herniation
            Level
            Approach
            T1-4
            Trans-sternal
            T2-6
            Right transthoracic
            T6-12
            Left or right transthoracic
      • Pros
        • Thoracotomy
          • Direct View of herniation and dural sheath (good for central disc herniation/calcified disc herniation)
            • Good for central disc or when myelopathy is present → best operative results
            • Good exposure obtained from T4–T5 to T11–T12
          • Complete decompression
          • Mini Thoracotomy
            • Lowers risk of thoracotomy related complications
          • Anterolateral transthoracic approach
          • Low risk of mechanical cord injury
          • Little compromise of stability
        • Thoracoscopy
          • Minimally invasive
          • Avoids pulmonary complications and morbidities
          • Less blood loss
          • Can access centrally located disc herniations
          • Prevents denervation of paraspinal musculature
          • Less bone resection
          • No stability comprise,
          • low risk mechanical cord injury,
       
      • Cons
        • Requires thoracic surgeon
        • Thoracotomy — high morbidity
          • Extensive, time-demanding procedure
          • Risk of vascular cord injury
          • Pulmonary complications and CSF pleural fistula
          • Postthoracotomy pain syndrome
          • Closed chest drainage is required postoperatively.
          • Mediastinal structures are at increased risk.
          • Hard to access discs above T4–T5
        • Thoracoscopy — extensive learning curve, view limited to the camera
          • Requires thoracic surgeon
          • High level of technical skill and steep learning curve
          • Limited ability to strut graft or fuse anteriorly
          • Difficult to repair CSF leak
      Posterolateral
      • Indication
        • Soft disc
        • Lateral disc
      • Pros
        • Can increase visualization by ligating nerve root
        • Can use angled endoscope to check anterior aspect of sheath if required
        • Avoid lung/chest related complications with anterior based approaches
      • Cons
        • Limitations on Extent of Exposure
        • Difficult access to central calcified disc herniations
        • Typically requires fusion
      Lateral
      • More lateral based approach and thus more visualization of anterior dura/disc herniation
      • Pros
        • Main advantage over anterior approach is that chest tube is not required
          • 30% rate of accidental pleural breach and thus negates major advantage of this approach
        • Enables total resection of centrally located discs
        • Good for central soft and calcified discs
        • Ease of multilevel exposure
        • No need for chest tube drainage if pleura preserved
      • Cons
        • Extensive procedures and bony resection
        • High operating times, blood loss
        • Significant perioperative pain and physiologic
        • stress to the patient
       
      Posterior
      • Laminectomy (Largely Abandoned)
  • Outcome
    • It is the authors’ experience that although patients may present with a long history of fixed neurological deficit due to delayed diagnosis, surgical decompression can still result in significant functional recovery.
    • There is no RCT data most data would suggest anterior approaches have poorer outcome than posterior lateral approaches. This is because anterior approaches are chosen for more difficult (central and calcified) disc cases.
    • Ridenour et al 1993
      • N=31, retrospective
      • Compared approach
      • One peri-OP neuro deterioration (lami)
      • No deterioration @ 15M
      • Concluded:
        • Abandon laminectomy
        • TP and CT both efficacious
    • Stillerman et al 1998
      • N=82, retrospective
      • Compared approach
      • Assessed for location (CL vs. L), calcification, & med. comorbidities
      • Results
        • 87% relief of pain
        • 84% relief sensory Sx
        • 76% relief B/B
        • 58% motor improvement
    • Hard to compare between different surgical approaches because type of disc herniation typically dictates approach
      • Neurological Outcomes all TDH post op (Hott 2005)
        • 53% improved
        • 42% stable
        • 5% worse
      • Complication rates by approach (Yoshihara)
        • 27% for anterior approach
        • 10% for posterior based approach
      • Any Central and Calcified Paracentral disc herniation (Berven/Ames)
        • Higher rate of neuro deterioration with posterior approach (19 x greater)
    • Posterior midline laminectomy:
      • 32% worse outcome,
      • 57% improved or stayed the same
    • Posterolateral approach:
      • 7% worse outcome,
      • 82% improved or stayed the same
    • Endoscopic transpedicular:
      • 90% improvement
    • Costotransversectomy:
      • 0% worse,
      • 12% same,
      • 88% improved
    • Anterolateral transthoracic approach:
      • 0% worse,
      • 94% pain improved,
      • 97% myelopathy improvement