6. Neuro (Spine) Flashcards
Spinal cord blood supply (8)
Anterior and posterior blood supply, both affected by different clinical syndromes.
Anterior spinal artery:
- arises bilaterally as 2 small branches at the level of the termination of the vertebral arteries.
- These 2 arteries join at the level of the foramen magnum
Artery of Adamkiewicz
- Most notable reinforcer of the anterior spinal artery.
- In 75% of people, it comes off the left side between T8 and L1.
- Supplies lower 2/3 of cord.
- Can get covered with placement of endovascular stent graft for aneurysm of dissection, leading to spinal infarct.
Posterior spinal artery
- Arises from either the bertebral arteries or the posterior inferior cerebellar artery
- Unlike the anterior spinal artery, this one is discontinuous and reinforced by multiple segmental or radiculopial branches.
Conus medulliaris (2)
Terminal end of the spinal cord.
Usually terminates at L1, below the inferior endplate of L2/3 should be sus for tethered cord.
Which nerve is compressed (5)
Other than C8 nerve, each pair of spinal nerves corresponds to a vertebra.
More than 90% of disc herniations occur at L4-5 and L5-S1.
At the L5-S1 disc:
- Foraminal disc will affect the exiting nerve, in this case L5.
- Central or Paracentral disc will affect the descending nerve, in this case S1
Epidural fat (3)
Epidural fat is not evenly distributed.
Epidural space in the cervical cord is predominantly filled with venous plexus (as opposed to fat).
In the lumbar spine, there is fat both anterior and posterior cord.
Spinal stenosis (5)
Can be congenital (associated with short pedicles) or acquired.
The Torg-Pavlov ratio can be used to diagnose (vertebra body width to cervical canal diameter <0.85).
Symptomatic stensosis is more common in the cervical spine (vs thoracic or lumbar).
Can get some congenital stenosis in lumbar due to short pedicles, but generally not symptomatic until middle age.
Disc nomenclature (5)
Focal herniation - herniated disc comprising less than 90 degrees of the disc circumference
Broad based herniation is a herniated disc between 90-180 degrees.
Protrusion is term used when distance between edge of the disc herniation is less than the distance between the edges of the base.
Extrusion is term used when edges of the disc are greater than the distance of the base.
Schmorl’s node (2)
Herniation of disc material through a defect in the vertebral body endplate, into the actual marrow.
Limbus vertebra (2)
Fracture mimic.
Result of herniated disc material between the non-fused apophysis and adjacent vertebral body
Scheuermann’s (2)
Multiple levels (at lest 3) of Schmorl’s nodes in the spine of a teenager, resulting in kyphotic deformity (40 degrees in thoracic or 30 degrees in thoracolumbar)
Enplate changes (5)
Commonly referred to as modic changes.
Progression in MRI signal:
- type 1 Starts with degenerative changes causing inflammation and oedeme (T2 bright).
- type 2 Progresses to chronic inflammation with some fatty change, causing T1 bright.
- type 3 Finally, all gets burned out and fibrotic (T1 and T2 dark).
Type 1 changes look a lot like osteomyelitis
Annular tears (3)
Tears in the dorsal annulus, usually T2 bright and curvilinear.
May be a source of pain (radial pain fibers trigger “discogenic pain”), also seen as incidentals.
Myelogram technique (4)
Contrast should flow freely away from the needle tip, gradually filling the thecal sac.
Outlining of the cauda equina is another promising sign of correct position.
Contrast pooling at the needle tip or along the posterior or lateral thecal sac, without free-flow, suggests injection into subdural space or into the fat around the thecal sac.
Precautions prior to LP (5)
Aspirin and NSAIDs are fine.
Hold heparin for 2-4hrs.
Hold LMWH for 12hrs
Hold clopidogrel for 7 days.
Hold warfarin for 4-5 days
Complications of spine surgery (6)
Recurrent residual disc
- lacks enhancement (unlike a scar which has delayed enhancement)
Epidural fibrosis
- Scar that is usually posterior and enhances homogenously
Arachnoiditis
- “Clumped nerve roots” and “empty thecal sac”.
- Enhancement for 6 weeks post op is normal, after is infectious or inflammatory
Conjoined nerve roots
- 2 adjacent nerve roots sharing an enlarged common sleeve, at a point during their exit from the thecal sac
Failed back surgery syndrome (3)
Defined as recurrent or residual low back pain in the patient after disk surgery.
Occurs about 40% of cases.
Causes of FBSS are grouped into early and late.
Jefferson fracture (4)
Burst fracture of C1 caused by axial loading. Blow is typically to top of head.
Anterior and posterior archest blow out laterally.
Neurologic cord damage is rare, all the force is directed to bones
Odontoid fracture classification (3)
Type 1: Upper part of odontoid, may be stable, rare
Type 2: Fracture at the base, unstable, by far most common.
Type 3: Fracture through dens into the body of C2. Unstable, but best healing prognosis
Os odontoideum (5)
Mimic of type 1 fracture of odontoid.
Ossicle located at the position of the normal odontoid tip (orthotopic position).
Base of dens is usually hypoplastic.
Prone to subluxation and instability, associated with Morquio’s syndrome
Orthotopic vs Dystopic: Orthotopic is position right on top of the dens, Dystopic is when it’s fused to the clivus.
Hangman’s fracture (5)
Seen most commonly when chin hits dashboard (direct blow to the face).
Bilateral pars fracture at C2, or the pedicles which is less likely.
Anterior subluxation of the C2 body.
Cord damage is uncommon, as the acquired pars defect allows for widening of the canal.
Often associated fracture of the anterior inferior corner at C2, from avulsion of the anterior longitudinal ligament.
Flexion teardrop (3)
Teardrop shaped fragment at the anterior-inferior vertebral body.
Flexion injury is bad because it’s associated with anterior cord syndrome (85% have deficits).
Unstable fracture, associated with posterior sublixation of the vertebral body.
Anterior cord syndrome (3)
Anterior portion of the cord affected.
Motor function and anterior column sensations (pain and temperature) are compromised.
Dorsal column sensations (proprioception and vibration) are still intact
Extension teardrop (2)
Anterior inferior teardrop shaped fragment with avulsion of the anterior longitudinal ligament.
Less serious than the flexion type
Flexion vs Extension teardrop (4)
Impaction injury vs distraction injury
Unstable vs maybe stable
Hyperflexion vs Hyperextension
Ran into wall vs hit from behind
Clay-shoveler’s fracture (4)
Avulsion injury of a lower cervical/upper thoracic spinous process, usually C7.
Due to forceful hyperflexion movement like shovelling.
Ghost sign describes double spinous process at C6-C7
Facet dislocation (2)
Spectrum of subluxed facets –> perched –> locked.
Can be unilateral or bilateral
Unilateral facet dislocation (3)
Usually due to hyperflexion and rotation.
Superior facet slides over the inferior facet and gets locked.
Unilateral is a stable injury.
Inverted hamburger sign on axial imaging on the dislocated side
Bilateral facet dislocation (4)
Due to severe hyperflexion.
Disruption of the posterior ligament complex.
Dislocated vertebra can be displaced forward one-half AP diameter of the vertebral body.
Highly unstable and strongly associated with cord injury
Atlantoaxial instablity (5)
Articulation between C1 and C2 allows for lateral movement of the head.
Transverse cruciform ligament straps the dens to the anterior arch of C1.
Distance between anterior arch and dens shouldn’t be more than 5mm.
Instability associated with Downs and Juvenile RA.
Rotary subluxaiton can occur in children, looks like torticollis.
May require dynamic movements while scanning to differentiate from torticollis.
Benign vs malignant compression fracture (6)
Retropulsed fragment vs convex posterior vertebral body cortex
Transverse t1 and t2 dark band for benign.
Malignant:
- Involves posterior elements.
- Epidural/paraspinal mass
- Multiple lesions
Trauma to cord (2)
Known correlation between spinal cord oedema lenght and outcome.
Most important factor for outcome is the presence of haemorrhagic spinal cord injury.
Spinal cord syndromes (6)
Central cord:
- Old lady with spondylosis or young with bad extension injury
- Upper extremity deficit is worse than lower (corticospinal tracts are lateral in lower extremity)
Anterior cord
- Flexion injury, causes immediate paralysis
Brown sequard
- Rotation injury or penetrating trauma.
- One half motor, other half sensory
Posterior cord
- Uncommon, sometimes seen with hyperextension
- Proprioception affected
Pars interarticularis defects (6)
Fatigue or stress fracture, probably developing in childhood.
Usually not symptomatic (25% are).
Commonest level is L5-S1, with the rest at L4-5.
Tend to have more spondylolisthesis and associated degenerative change at L4-5 than L5-S1.
Can be seen on oblique plain film as a collar on the scottie dog.
Pars defects with anteriorlisthesis will have neuroforaminal stenosis, with spinal canal widening (when severe, will have spinal canal stenosis also).
Terminal ventricle (6)
aka ventricularis terminalis.
Developmental variant.
Normally, a large portion of the distal cord involutes in a late stage of spinal cord embryology.
Sometimes, this process is not uniform, and a cyst forms at the end of the cord.
This is usually small (4mm) and causes no symptoms.
Sometimes they get very big and cause neurilogic symptoms.