Module 6 - The Neck and Spine Part B PDF

Week 9 – The neck and spine The spine Module overview Neck Anatomical triangles of the neck Longitudinal compartments of the neck Spine Bony structures of the spine Musculature of the spine The spinal cord Imaging of the neck and spine NOTE - Anatomical co...

Week 9 – The neck and spine The spine Module overview Neck Anatomical triangles of the neck Longitudinal compartments of the neck Spine Bony structures of the spine Musculature of the spine The spinal cord Imaging of the neck and spine NOTE - Anatomical content covered in 1st and 2nd year Today’s lecture extends upon topics covered in BMSC11007, BMSC11008, and BMSC12007 When these topics are re-presented during this lecture they are presented as a summary as time does not permit a detailed discussion You should however go back and revise this content in detail as it will be assumed knowledge and is examinable Just to be clear…. The neck and spine were major topics in BMSC11007 and BMSC11008. There were numerous lectures covering Musculoskeletal anatomy – including bony landmarks Neurovascular supply - including spinal nerves BMSC12007 was also an entire unit dedicated to the nervous system As such the content delivered in these units is assumed knowledge, we do not have time to recap this content in depth during BMSC13022 You are expected to know this to the level of detail presented in these first and second year units The spine – bony structures Comprised of 33 vertebrae with associated intervertebral disc 7 cervical 12 thoracic 5 lumbar 5 sacral (fused) 4 coccyx (fused) The spine – bony structures Typical vertebrae contain Body Pedicle Vertebral foramen – houses the spinal cord Vertebral arch Transverse process Spinous process Lamina Superior and inferior articular process Superior and inferior vertebral notch Anatomical comparisons between vertebral regions C1 and C2 vertebrae The C1 and C2 vertebrae have unique features that enable them to accommodate movement of the head No intervertebral disc between these two vertebrae C1 (aka the atlas) Directly articulates with the head using the facets for the occipital condyle Lacks a vertebral body Contains two lateral masses connected by anterior and posterior arches Also contains articulation point with the dens C2 (aka the axis) Most notable feature is the dens which acts as a pivot point for side to side movement of the head C1 and C2 vertebrae – ligaments The joint between the C1 and C2 vertebrae are stabilized by several ligaments Transverse ligament of atlas Alar ligaments Apical ligament of dens The spine – foramina The vertebral foramina create a longitudinal vertebral canal which houses the spinal cord Inferior and superior vertebral notches of successive vertebrae create intervertebral foramen on each side of the spine Allow spinal nerves and blood vessels to pass into / out of the vertebral canal The spine – joints Two major types of joints exist between successive vertebrae Symphyses – between superior and inferior surfaces of successive vertebrae This joint also includes the intervertebral discs which are fibrocartilaginous structures that serve as shock absorbers Have their own unique anatomy Anulus fibrosis Nucleus pulposus Synovial – between articular processes and known as zygapophysial joints The spine – ligaments Several ligaments serve to stabilize and support the vertebral column including Anterior and posterior longitudinal ligaments Liagmenta flava Supraspinous ligament and ligament nuchae Interspinous ligaments The spine – ligaments Anterior and posterior longitudinal ligaments – located on anterior and posterior surfaces of the vertebral bodie The posterior longitudinal ligament lines the anterior surface of the vertebral canal Liagmenta flava – connect posterior surface of the lamina on the vertebra below to the anterior surface of the lamina of the vertebra above The spine – ligaments Supraspinous ligament and ligament nuchae – the supraspinous ligament connects the spinous processes of CVII vertebrae to the sacrum Above the CVII vertebrae a thick triangular ligament known as the liagmentum nuchae connects the cervical vertebrae to the skull Interspinous ligaments – connect adjacent vertebral via the spinous processes Curvatures of the spine When viewed from the side the spine has primary and secondary curvatures Primary – present during fetal development Described as kyphotic curves Convex posteriorly and concave anteriorly Include thoracic and sacral/coccygeal curvatures Secondary – form after birth Described as lordotic curves Concave posteriorly Include cervical and lumbar curvatures The spine – musculature Muscles within the back can be classified as either extrinsic or intrinsic Alternatively they can be classified as either superficial, intermediate or deep Extrinsic muscles are involved with movements of the upper limbs and thoracic wall Generally innervated by anterior rami of spinal nerves Include the superficial and intermediate muscles Intrinsic muscles are situated deeper to the extrinsic muscles serve to support and move vertebral column and head Innervated by posterior rami of spinal nerves Include all the deep muscles of the spine Spinal muscles – superficial Extrinsic muscles include Superficial group Latissiums dorsi Trapezius Levator scapulae Rhomboid major Rhomboid minor The later three muscles are deep to the trapezius Spinal muscles – intermediate Extrinsic muscles include Intermediate group Serratus posterior superior Deep to the rhomboid muscles Serratus posterior inferior Deep to the latissimus dorsi Spinal muscles – deep Intrinsic muscles include Deep group Spinotransversales muscles Splenius capitis Splenius cervicis Erector spinae Iliocostalis Longissimus Spinalis Transversospinales Semispinalis Multifidus Rotatores Segmental muscles Suboccipital muscles The spine – posterior muscles of the neck Earlier in this module we discussed the vertebral compartment in the neck and said it was largely comprised of vertebrae and muscles including Sternocleidomastoid Anterior, middle and posterior scalenus Longus colli Muscles of the spine including Trapezius Levator scapulae Spinotransversales muscles Transversospinalies muscles Now that we have discussed the muscles of the spine lets identify those that are located in the posterior neck The spine – posterior muscles of the neck Notably not all spinal muscles are located in the neck Using the superficial, intermediate and deep classification system we just covered, the muscles which can be located in the posterior neck are highlighted below Superficial group Deep group Latissiums dorsi Spinotransversales Trapezius muscles Splenius capitis Levator scapulae Splenius cervicis Rhomboid major Erector spinae Rhomboid minor Iliocostalis Longissimus Spinalis Transversospinales Intermediate group Semispinalis Serratus posterior superior Multifidus Rotatores Serratus posterior inferior Segmental muscles Suboccipital muscles The spine – spinal cord The spinal cord Lies within the vertebral canal which is created by Anterior wall – vertebral bodies Lateral walls and roof – vertebral arches and ligaments Is surrounded by meninges which are continuous with meninges of the brain Pia Arachnoid Dura Has a cervical enlargement around C5-T1 Generally tapers to an end at L1 – L2 level End point of the spinal cord known as conus medullaris and is anchored to the coccyx via the filum terminale Nerve roots from L1-S5 continue to pass down through the vertebral canal forming a structure known as the cauda equina The spine – spinal cord The external surface of the spinal cord is marked by several fissures including Anterior median fissure Posterior median sulcus Posterolateral sulci Internally the spinal cord has a central canal surrounded by Grey matter White matter The spinal cord – vasculature Blood supply to the spinal cord is via Anterior spinal artery Posterior spinal arteries The spine – spinal nerves 31 pairs of spinal nerves emerge from the vertebral canal between the pedicles 8 pairs of cervical 12 pairs of thoracic 5 pairs of lumbar 5 pairs of sacral 1 pair of coccygeal The spine – spinal nerves Each contains anterior and posterior root Anterior roots contain efferent nerve fibers (including motor and autonomic neurons) and their cell bodies are located in the central grey matter of the spinal cord Posterior roots contain afferent nerve fibers (including sensory neurons) and their cell bodies are located in the dorsal root ganglion The anterior and posterior roots fuse together forming a mixture of sensory, motor and autonomic fibers and then branch to form the anterior and posterior rami Imaging of the neck and spine X-rays, CTs and MRIs are common imaging modalities of the neck and spine Interpreting these images relies on having solid understanding of the associated anatomy and use of a systematic approach One such system for interpretation uses ABC as a pneumonic to systematically assess spinal images. Where this stands for A - alignment B - bones C - cartilage ABC of spine images Alignment When viewing medical images of the spine there are multiple lines you need to assess for alignment Lateral view Anterior longitudinal line (yellow) – runs along the anterior surface of the vertebral bodies Posterior longitudinal line (orange) – runs along the posterior surface of the vertebral bodies Spinolaminar line (red) – runs along the anterior edge of the spinous processes AP view Lateral lines (yellow) – either side of the vertebral bodies Spinous process line (blue) – runs through each spinous process Noting that misalignment can indicate a fracture or displacement ABC of spine images Bones Carefully inspect the cortex of every bone in a systematic way (eg top to bottom) to ensure it is continuous and there is no loss of vertebral height Loss of height can be suggestive of a fracture Also assess the vertebral endplates, pedicles, laminae and spinous processes to ensure they are uninterrupted ABC of spine images Cartilage Intervertebral discs should increase in size as you progress inferiorly down the spine Note however the L5/S1 space is normally slightly narrower than L4/L5 Also keep in mind if there are concerns about disc integrity / protrusion x-ray is not a suitable imaging modality and MRI is preferred Normal cervical anatomy Normal thoracolumbar anatomy Normal spine anatomy Spine pathologies Ankylosing spondylitis (inflammatory arthritis of the spine) Spondylosis (degenerative disc disease) Fractures Three column model Spondylolysis Spondylolisthesis Bulging and herniated discs Cauda equina syndrome Abnormal curvature of the spine Kyphosis Lordosis Scoliosis Ankylosing spondylitis Ankylosing spondylitis is inflammatory arthritis of the spine Results in fusion of the spine and sacroiliac joints Radiographic appearance is variable depending on stage of disease (early vs late) In latter stages, diffuse changes give “bamboo spine” appearance of the vertebrae and “dagger spine” appearance of the interspinous ligament Spondylosis Spondylosis involves degeneration of the intervertebral disc space leading to narrowing, endplate sclerosis and osteophyte formation AKA age related disc degeneration In some cases osteophytes can cause neural impingement  Three column model of spinal fractures Divides the spine into three vertical columns Anterior Anterior longitudinal ligament Anterior 2/3 of the vertebral body Anterior 2/3 of the intervertebral disc Middle Posterior 1/3 of the vertebral body Posterior 1/3 of the intervertebral disc Posterior longitudinal ligament Posterior Everything posterior to the posterior longitudinal ligament Instability occurs when an injury affects 2 or more contiguous columns You do not need to identify the sub-types of spinal fractures on imaging for this unit – just be aware of Spondylolysis Spondylolysis occurs when a fracture (acute or chronic) extends from the inferior facet across the pars interarticularis (area of the lamina that lies within the facets), to the superior facet On a oblique radiograph appears as a “Scotty dog” where the features of the dog represent Nose - transverse process Eye – pedicle Ear – superior facet Front leg – inferior facet Neck – pars interarticularis Collar across the neck – fracture This defect can is some cases be bilateral and lead to spondylolisthesis Spondylolisthesis Spondylolisthesis occurs when one vertebra is displaced forward upon another This can occur secondary to trauma or as a result of degenerative disease such as osteoarthritis If severe it may lead to foraminal stenosis, causing nerve root impingement Summary of pathologies covers so far…. Also note that sondylosis (not shown here) is age related degeneration of the spine Bulging and herniated discs Bulging disc – the outer annulus fibrosis remains in tact however protrudes into the spinal canal causing compression of a nerve root or spinal cord Herniated disc – the nucleus pulposus protrudes through a tear in the annulus fibrosis causing compression of a nerve root or spinal cord Cauda equina syndrome Medical emergency that results when the descending lumbar and sacral nerve roots are compressed Commonly caused by herniated lumbar disc Symptoms can manifest as Perianal (saddle) paraesthesia May also include weakness of the lower limbs Reduced / absent lower limb reflexes Unilateral / bilateral radiculopathy or sciatica Lower back pain Bowel, bladder and / or sexual dysfunction Abnormal curvature of the spine Sometimes the natural curvature of the spine does not align properly or is exaggerated, potentially resulting in Kyphosis – A rounding of the spine in the upper back. It can look like you have a hump in your back Lordosis – An increased curve toward the front of your body in your lower back or neck area Scoliosis – The spine curves from side to side in an S-shape or C-shape rather than being straight Kyphosis Scoliosis Prescribed reading Chapters 2 and 8 of Greys anatomy for students Chapters 1 and 2 of Abrhams and McMinn’s Clinical atlas of human anatomy