Spine structured oral questions5: Lumbar spinal stenosis and cervical myelopathy

EXAMINER: A 70-year-old lady has been referred to your clinic having been seen by one of your arthroplasty colleagues. Her walking distance had reduced significantly but no abnormalities of her hips had been found and this MRI scan had been requested. Can you see anything that might cause this lady’s symptoms?

(Figure 5.6.)

CANDIDATE: Yes. The images are T2-weighted MRI scans showing the lumbar spine in axial and sagittal section. Both sagittal and axial scans show significant narrowing of the spinal canal, judging from the sagittal scan this appears to be at the L4/5 level.

EXAMINER: Yes, there is a very significant spinal stenosis at that level with obvious compression of the thecal sac surrounding the cauda equina and significant reduction of the CSF signal on the axial scan. How does this kind of stenosis arise and what neurological abnormalities are you like to find on examination?

CANDIDATE: Neurological examination of patients with lumbar spinal stenosis is often remarkably normal. The stenosis arises as a consequence of dehydration of the intervertebral disc leading to bulging of the disc, overload and hypertrophy of the facet joints, segmental instability and hypertrophy of the ligamentum flavum and osteophyte formation.

EXAMINER: Okay, so how do these patients typically present, and what will you be looking for on examination?

Figures 5.6a and 5.6b T2-weighted MRI axial and sagittal images of lumbar stenosis.

CANDIDATE: Patients with symptomatic lumbar spinal stenosis typically present with neurogenic claudication. Neurogenic claudication is a reduction in walking distance as a result of bilateral aching leg pain, a feeling of heaviness, fatigue, numbness and unsteadiness in the lower limbs. Symptoms are frequently reduced by rest and bending forward. Bending forward flexes the lumbar spine, reducing the lumbar lordosis, and increases the space available for the cauda equina within the spinal canal. Activities that involve flexion of the lumbar spine (e.g. walking uphill, upstairs, pushing a shopping trolley and cycling) are frequently found to be easier than less arduous tasks that extend the lumbar spine (increasing the lordosis).

The most common differential diagnosis is vascular claudication. Clinical examination with palpation of peripheral pulses as well as ankle–brachial pressure measurement is required. Standing relieves vascular claudication whereas neurogenic claudication may be made worse.

EXAMINER: Here is an MRI scan showing severe narrowing of the cervical spinal canal. Is this likely to present in the same way? (Figure 5.7.)

CANDIDATE: No, in this case we are at the level of the spinal cord rather than the cauda equina. There is a bulging cervical disc at the (most common) C5/6 level and the patient will present with symptoms of cervical myelopathy.

EXAMINER: What are the typical features of cervical spondylotic myelopathy and what would you expect to find on examination?

CANDIDATE: Cervical myelopathy presents with upper motor neurone signs and symptoms in both upper and lower limbs. Symptoms include decreased coordination, loss of fine dexterity (e.g. buttoning a shirt, handwriting, manipulating small objects), balance and gait problems, and problems with bowel and bladder function. Typically symptoms follow a slow, progressive course deteriorating in a stepwise manner with stable periods and periods of rapid deterioration. Balance and walking problems may lead to patients complaining of frequent trips, falls or bumping into things.

Associated (upper motor neurone) signs include: a wide based unsteady gait, upper and lower limb weakness, hyper-reflexia, intrinsic muscle waiting in the hand, positive Babinski and Hoffman signs and an inverted radial reflex.

Stenosis background knowledge

Lumbar spinal stenosis can occur within the spinal canal, the lateral recesses or the intervertebral (neural exit) foramen. Central stenosis may be asymptomatic

Figure 5.7 T2-weighted sagittal MRI image demonstrating cervical stenosis.

or it may give rise to the symptoms of neurogenic claudication. Lateral recess stenosis or foraminal stenosis may lead to unilateral or dermatomal symptoms. Stenosis is frequently associated with a degenerative spondylolisthesis (which will be discussed in more detail in the next section).

Distinguishing between neurogenic claudication and vascular claudication:

Hoffman’s sign – Flicking the distal phalanx of the middle finger produces reflex contraction of thumb and index finger.

Babinski’s sign – Extension of the toes on scraping/firmly stroking the sole of the foot.

Anterior approach to the cervical spine

Many right-handed surgeons prefer the right-sided approach. The left-sided approach has been reported as having a lower rate of recurrent laryngeal nerve injuries. Consider using a foot rest and tapes over the shoulders (acromion) to allow as much of the cervical spine to be exposed as possible for lateral imaging. The head is positioned on a horseshoe ring and neck is in slight extension(towel rollbetween shoulders). The skincrease incision is made in line with the following landmarks.

C3/4 – Hyoid bone

C4/5 – Laryngeal prominence

C5 – Thyroid cartilage C6 – Cricoid cartilage

Platysma is incised in line with the skin incision and the fascia dissected to expose the medial border of sternocleidomastoid. The plane between the larynx and oesophagus medially and the carotid sheath laterally is dissected using blunt dissection. The omohyoid muscle is retracted or divided. Pre-cervical fascia is divided medial to the neurovascular bundle and further blunt dissection exposes the longus colli muscles. These are elevated and a retractor placed. The intended spinal procedure can then be undertaken.

Anterior cervical decompression and fusion provides excellent results and has a low complication rate. The anterior approach allows access to the cervical disc that can be removed along with osteophytes at the posterior aspect of the vertebral body. It allows removal of most lesions causing myelopathy or radiculopathy. Placement of anterior bone graft between the vertebral bodies in the excised disc space helps to decompress the exit foramen indirectly and facilitates fusion.

Complications include pseudarthrosis ( increased in smokers), hoarse voice and swallowing problems caused by retraction or injury to the recurrent laryngeal nerve (2–5%). This may also be caused by placement of the ET tube (more common). Graft complications also include the graft loosening and migration. Fusion alters the mechanics of the cervical spine, increasing the lever arms of forces acting at adjacent levels, and there is a significant rate of adjacent level degeneration.

One contributing cause of cervical stenosis may be ossification of the posterior longitudinal ligament, particularly in Japanese individuals.

Cervical disc replacement

Cervical disc replacement is a newer technique which treats similar pathologies through the same anterior approach but attempts to preserve motion in the cervical spine by replacing the cervical disk with materials similar to those used in large joint arthroplasty. Initial results are encouraging.¹

1. Murrey D, Janssen M, Delamarter R et al. Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1- level symptomatic cervical disc disease. The Spine J 2009;9:275–286.