The spinal cord contains lower motor neurons, first-order sensory neurons, second-order spinothalamic neurons, interneurons, as well as the ascending and descending tracts that connect these cells with the brain. The spinal cord is surrounded by the vertebral column, which consists of a number of discrete bones called the vertebrae. Each vertebra consists of a cylindrical bone anteriorly called the body, two lateral processes called transverse processes, and a dorsal process called the spinal process. The transverse processes are connected to the vertebral body by the pedicles and to the spinous process by the laminae. The hollow in the ring is formed by the posterior vertebral body, pedicles, laminae, medial transverse process and anterior spinous process forms part of the spinal canal. The successive vertebrae articulate with one another intervened by discs and facet joints (Figure 38-1).
The spinal cord is segmentally organized. These segments correspond embryologically to the nerve supply of somites, which give rise to the musculature. There are 31 spinal cord segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each segment corresponds to a spinal nerve. These nerves are named after the segment from which they originate. C1–7 exist in the spinal canal above their corresponding vertebrae and the rest exist below their vertebrae. The spinal cord ends at the level L1, so that with more caudal segments the distance between the spinal segment and the point of exit of the spinal nerve from the vertebral column increases. In the lumbar vertebral column, the spinal roots have to travel a distance to reach their point of exit. The mass of stringy roots travelling in the lower vertebral column resemble a horse’s tail or cauda equina.
The spinal cord is supplied by one anterior and two posterior spinal arteries. The anterior spinal artery is formed from branches of the vertebral artery and runs caudally along the anterior fissure of the spinal cord, while two paired posterior spinal arteries travel in the dorsolateral sulci. Segmental arteries supply and supplement the blood in the spinal arteries. The most significant of these radicular arteries is the artery of Adamkiewicz.
The cross section of the spinal cord is characterized by a central area of an “H”-shaped gray matter surrounded by white matter. The gray matter has two dorsal horns that serve predominantly a sensory role, two anterior horns that contain motor neurons and interneurons, and an intermediate gray that intervenes between the two on the lateral side and contain autonomic cells. The area around the central canal (which is continuous with the ventricular system) is called central gray. The gray matter divides the white matter into anterior, lateral, and posterior segments. The posterior “column” contains the spino-lemniscal pathway, which mediates fine touch, vibration, and proprioceptive modalities. The signals from the lower limb travel via fasciculus gracilis and those from the upper limb via fasciculus cuneatus. The lateral column contains the lateral corticospinal, as well as ventral and dorsal spinocerebellar tracts. The spinothalamic tracts travel in the anterolateral portion of the spine (Figure 38-2).
CASE 38-1
A 64-year-old woman presents with 6 weeks of back pain and progressive gait disorder. The patient first noticed the presence of sensory changes in the feet. A few weeks later she had her first fall and noticed the ascent of leg numbness. This morning, she noticed difficulty getting out of her chair and had a number of urinary accidents. On examination, the patient has a sensory level to the umbilicus with reduction of both pain/temperature and touch/vibration to roughly the same level. The muscle stretch reflexes are increased in the knees and the ankles but not for triceps or biceps. On motor testing, there is 2/5 strength (Medical Research Council [MRC] grading) involving all the muscles of the lower limb. The bladder scan shows 300 mL of urine. There is sacral sparing.
Myelopathy simply means disorder of the spinal cord and is often characterized by:
Multisegmental weakness (grades 0–2)
Changes in muscle stretch reflexes: less brisk acutely, and more so chronically
Ataxia of limbs or trunk
Sensory levels
Lhermitte’s phenomenon—shock-like or electrical sensation with passive neck flexion
Bowel and bladder dysfunction
Autonomic dysfunction
The localization of spinal cord lesion involves two components:
What part of the cord in cross section is involved
Complete cord syndrome—the whole cord is involved
Incomplete cord syndromes:
Hemi-cord or Brown-Séquard—only one half of the cord on one side of the midline is involved.
Subacute combined degeneration of the cord (SCD)—both dorsal columns and the corticospinal tracts are involved.
Anterior cord syndrome—see below
Posterior cord syndrome
Central cord syndrome
Dorsal root ganglion syndrome (placed here for comparison)
What is the highest segmental level of involvement
Cervico-medullary level
Cervical, thoracic, or lumbar level
Cauda equine syndrome
Conus medullaris syndrome
What are the three pieces of information needed to ascertain the extent of the cross sectional involvement of the cord?
The involvement of spinothalamic (ST), dorsal column (DC), and lateral corticospinal tracts (CS) is the minimum information needed for this. The different permutations are as follows (Table 38-1):
Bilateral involvement of ST + DC + CS: likely complete cord syndrome
Segmental unilateral involvement of ST + DC: likely dorsal root ganglion
Bilateral involvement of ST + CS: likely anterior cord syndrome
Bilateral involvement of DC + CS: likely SCD
Involvement of DC only: likely posterior cord syndrome
Bilateral ST only: likely central cord syndrome
Ipsilateral DC + CS, contralateral ST: Brown-Séquard syndrome
The level of the lesion is the most caudal normal level (not the most rostral abnormal level)—that means that if, for example, L1 and below are dysfunctional, the level is L2.
After determining the levels for each of DC, ST, and CS separately, the highest level is likely to be the correct one.
Upper motor neuron signs and symptoms are useful in chronically evolving lesions but, due to spinal shock, are absent in acute lesions.
The American Spinal Injury Association (ASIA) provides a clinical tool that helps with determining the levels for DC, ST, and CS (see Figure 15.5—Neurotrauma and Myelopathies).
Bowel and bladder dysfunction is common in myelopathies. This is due to the disruption of ascending and descending pathways, which carry 4 types of information to and from the bladder: autonomic afferent, autonomic efferent, somatic sensory, and somatic motor. Postvoid bladder scan may be used as a measure of bladder atony in acute spinal cord injury. Arbitrarily the cutoff is set at 200 mL. At 500 mL and above, retention can cause obstructive nephropathy. Catheter is placed to relieve the retention. Postobstructive diuresis occurs because of renal tubular dysfunction caused by the obstruction. The fluid and electrolytes should be replaced during the period of polyuria.
Sacral sparing is the maintenance of motor (anal wink, bulbo-cavernosus reflex, or priapism) or sensory (deep anal pressure) function. The presence of sacral sparing is a good prognostic sign.
Grades 0–2 are classified as weak.
ASIA Impairment Scale (AIS):
A = Complete. No sensory or motor function is preserved in the sacral segments S4–S5.
B = Sensory incomplete. Sensory but not motor function is preserved below the neurological level and includes the sacral segments S4–S5 (light-touch, pinprick at S4–S5: or deep anal pressure (DAP)), AND no motor function is preserved more than 3 levels below the motor level on either side of the body.
C = Motor incomplete. Motor function is preserved below the neurological level, and more than half of key muscle functions below the single neurological level of injury (NLI) have a muscle strength grade less than 3 (MRC Grades 0–2).
D = Motor incomplete. Motor function is preserved below the neurological level, and at least half (half or more) of key muscle functions below the NLI have a muscle grade >3 (MRC).
E = Normal. If sensation and motor function as tested with the ISNCSCI are graded as normal in all segments, and the patient had prior deficits, then the AIS grade is E. Someone without an initial SCI does not receive an AIS grade.
It is valuable for prognostication.
Complete and incomplete spinal syndromes occur due to a number of mechanisms:
Transection: This is often a result of trauma, blunt or penetrating.
Compression: Compression can damage spinal tissue by direct mechanical pressure but mostly through disruption of venous drainage and arterial supply, causing cord infarction. The etiologies include:
Tumors—for more details, see below.
Spondylopathies—bony, ligamentous, and disc-related masses.
Other space-occupying masses—hemorrhage or abscess.
Inflammation:
Demyelinating disease (Figure 38-3; also see Chapter 43 Demyelinating Diseases)
Infection
Paraneoplastic disease
Radiation myelopathy
Metabolic problems—See below.
Cord Ischemia—arterial or venous.
Given that a metastasic tumor is the most likely cause of this presentation, is it likely to be an extramedullary or an intramedullary lesion?
This is most likely an extramedullary compression because of (Table 38-2):
Pain: Radicular and bony pain are more common in extramedullary lesions.
Upper motor neuron signs: Early in extramedullary, later in intramedullary.
Lower motor neuron signs: More common in intramedullary.
Progressive sensory symptoms: Ascending in extramedullary and descending in intramedullary.
Different Presentations of Intramedullary and Extramedullary Tumors
| Symptoms/Signs | Intramedullary Tumors | Extramedullary Tumors |
|---|---|---|
| Radicular pain | Unusual | Common, may occur early |
| Vertebral pain | Unusual | Common |
| Funicular pain | Common | Less common |
| Upper motor neuron signs | Yes, late | Yes, early |
| Lower motor neuron signs | Prominent and diffuse | Unusual, if present, segmental distribution |
| Paresthesiae progression | Descending progression | Ascending |
| Sphincter abnormalities | Early with caudal lesions (conus/cauda equina) | Late |
| Trophic changes | Common | Unusual |
The presence of symptoms in cord compression are initially the result of dysfunction, which may be reversed by decompression of the cord. After a period of time, which depends on the chronicity of compression, the cord infarcts secondary to venous congestion and arterial insufficiency. Once this occurs, the deficits are irreversible.
Brown-Séquard syndrome: Brown-Séquard syndrome is the name applied to an incomplete myelopathy affecting one lateral half of the cord in cross section. It presents with motor and dorsal column signs on the ipsilateral hemibody below the level of the lesion and contralateral dysfunction in the spinothalamic domain several segments below the level of the lesion. It is caused by the same pathologies that cause complete myelopathies. Prognosis is significantly better than complete cord syndrome.
Central cord syndrome: Central cord syndrome is caused by dysfunction of the central cord, as the name suggests, and involves variable sensory changes below the level of the lesion, upper limb more than lower limb weakness, and bladder dysfunction. It is most commonly caused by hyperextension injury of the neck causing cord concussion or contusion. Any mass or demyelinating lesion, or a very large syrinx may produce the same symptoms. When caused by cord concussion or contusion, the prognosis is often very good.
Syringomyelia: Caused by congenital anomalies (such as Chiari malformation), tumor, trauma, or inflammation (eg, syphilis or MS), this is an enlargement of the central canal of the spinal cord. The most common symptom is a suspended pain and temperature loss (ie, normal sensation below and above the area of change) due to the compression of the spinothalamic fibers crossing in the anterior white commissure. When the syrinx is in the neck, its most common place of occurrence, the suspended sensory loss is described as cape-like, that is involving the shoulders and the upper limbs. When syrinx is larger, it can affect motor and autonomic functions also.
Anterior cord syndrome: Anterior cord syndrome is caused by infarction or ischemia of the area of supply of the anterior spinal artery supplying the anterior two thirds of the cord. Spinothalamic and corticospinal functions are affected below the level of the lesion but fine touch, vibration, and proprioception are intact. The syndrome can be caused by vascular causes affecting the anterior spinal artery (such as vasculitis) but is most commonly caused by insufficiency of segmental arteries due to aortic disease such as aneurysms or dissection. Anterior compression (disc, spondylosis, or neoplasm) can also cause compression of the anterior spinal artery and loss of blood supply.
Posterior cord syndrome: Posterior cord syndrome is caused by selective loss of posterior column function. The classic cause of this is tabes dorsalis caused by tertiary syphilis. Vascular causes affecting the posterior spinal arteries are rare. When unilateral, the difference between it and dorsal root ganglion pathology is that in the latter, spinothalamic tracts are also affected.
Subacute combined degeneration of the cord: This is caused by B12 deficiency, nitrous oxide (NO) toxicity, copper deficiency, or zinc toxicity and affects the dorsal column and the corticospinal tracts. Less commonly, HIV myelopathy, HTLV infections, and spinal stenosis can present in a similar way.
Cervical: Cervical lesions can cause significant disability and may lead to quadriplegia aka tetraplegia and sometime loss of ability to breathe independently. Autonomic dysfunction can also occur.
High cervical lesion: A lesion of C1–3 can cause significant problems with diaphragmatic function and may necessitate mechanical ventilation.
Low cervical lesion: These affect arm functions. Complete myelopathy above the level of C7 prevents the patient from carrying out BADLs and may make her dependent on institutional care.
Thoracic: This leads to paraplegia (aka diplegia) as well as bowel and bladder dysfunction. Clinically, these may be divided into two groups:
T1–T8:
Because of the inability to control trunk muscles, the patient has trunk instability and cannot sit independently.
Like cervical lesions, autonomic dysreflexia can occur. This is when the sensory stimulation (often pain) from below the level of the lesion leads to hypertensive crisis.
T9–12: These patients have trunk stability.
Lumbar: Some proximal muscle function may be preserved depending on the level.
Conus medullaris and cauda equina: These conditions are often treated together because they are sometimes mistaken with one another on clinical grounds. There are 3 major differences between the 2 that accounts for their chronic clinical presentation differences:
Conus medullaris is an upper motor neuron and myelopathic process, whereas cauda equinais a lower motor neuron and peripheral process. This means that radicular pain and asymmetry may be seen in cauda equina, whereas symmetry and autonomic signs are more common in conus medullaris lesions.
Conus medullaris is caused by vertebral levels L1–2 corresponding to spinal levels S1–5, whereas cauda equina is caused at vertebral levels >L2 corresponding to the spinal roots of L1–S5. Both ankle and knee reflexes are affected in cauda equina, whereas only ankle jerks are affected in conus medullaris lesions.
Conus medullaris occupies a small physical space in comparison to cauda equina, so the symptoms of conus medullaris are, by comparison, more sudden and symmetrical.
Intradural intramedullary:
The majority are ependymomas:
Myxopapillary ependymomas (Grade I) occur mostly on filum terminale and can give rise to conus medullaris syndrome.
Cellular ependymomas (Grades II and III) occur within the central canal of the spinal cord. Both have good prognosis with resection and radiation.
Low-grade astrocytomas:
Fibrillary astrocytoma (grade II)
Anaplastic (grade III)
Glioblastoma (grade IV)
Surgery is the most important part of the treatment. With grade II lesion, after complete resection the patient may be monitored clinically and radiologically. Otherwise surgery is followed by radiation. Chemotherapy is largely palliative.
Metastases—uncommon to the cord itself. Most are lung, lymphoma, renal cell, melanoma, adenocarcinoma of unknown primary, and lymphoma. Often presents as Brown-Sequard syndrome and progresses rapidly. It has a poor prognosis: survival is of the order of 3–4 months. Given this, one may either do nothing, treat with steroids, or use radiation.
Hemangioblastomas—in von Hippel-Lindau syndrome (Figure 38-4).
Intradural extramedullary:
Meningiomas have a strong female predominance. Complete resection is often curative. If resection is incomplete then it should be followed by radiation therapy.
Schwannomas: These arise from Schwann cells mostly in the dorsal root ganglion (DRG). When they occur as a part of neurofibromatosis type 2 syndrome, they have a capacity to become malignant. They present with DRG syndrome (DC + ST) but may progress to cord compression or cauda equina syndromes.
Neurofibromas: These are also nerve sheath tumors, but in addition to Schwann cells, they incorporate connective tissue and neurons also. Their risk of malignant transformation is increased if they are part of neurofibromatosis type 1 syndrome. They can occur in two forms:
Solitary—These are benign and cured by resection.
Plexiform—These affect multiple roots and have dysmorphic nerve bundles incorporated within them. They have the capacity to become malignant and, in addition to surgery, may require radiation and chemical therapies.
Extradural:
Neoplastic seeding of the leptomeninges, depending on the type of tumor involved, is called carcinomatosis, lymphomatosis, or gliomatosis. The most common tumors are breast cancer, lung cancer, melanoma, lymphoma, and acute leukemia. The patient may present with a combination of radiculopathy, myelopathy, or cranial neuropathy. It is difficult to diagnose as contrasted MRI and CSF cytology both have high false-negative rates. Treatment is with intrathecal or systemic chemotherapy. Intrathecal chemotherapy may be administered with a lumbar puncture or with a subgaleal reservoir.
Epidural mass: Epidural masses may be caused by vertebral or epidural metastases. There is often bony vertebral pain, which is worse at night and with movement.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
