A Fall Brings the Answer
The patient, a 74-year-old retiree, had never been seriously ill before. Two years before admission, he began to have trouble walking. His legs felt stiff and he could not lift his feet fully off the ground, so that he shuffled while walking and sometimes fell. He thought this might be normal for his age and did not seek medical attention. He secretly feared he might have Parkinson disease, of which his father had died at age 75 years.
His gait rapidly worsened in the months before admission. He could no longer feel the soles of his feet when walking barefoot, and he had a strange sensation of walking on cotton. He fell more often. He also developed more frequent minor injuries on his feet, some of which he failed to notice. Finally, a fall led to a comminuted forearm fracture, and he was admitted to the hospital.
The orthopaedists repaired the fracture surgically and consulted a neurologist, who took a thorough history and performed a neurologic examination. The patient said that he had fallen more often in recent months and also (in response to a specific question) that he had sometimes failed to get to the toilet on time. His bladder control was poor at the moment, “but, after all, I have prostate trouble, too.” Further questioning brought out the family history of Parkinson disease.
On examination, there were no abnormalities of the head, cranial nerves, spine, or upper limbs, and there was no rigidity or tremor. Rapid alternating movements were dexterous. There was, however, a marked diminution of sensation to light touch and, to a lesser extent, of pain, from the level of the umbilicus downward. The lower limb extensors were spastically hypertonic. The knee- and ankle-jerk reflexes were brisk, with pathologic spreading. Babinski signs were present bilaterally.
The patient’s symptoms, age, and family history had made the orthopaedists think of Parkinson disease. The classic triad of hypokinesia/akinesia, rigidity, and tremor was missing, but repeated falls are indeed common in atypical parkinsonian syndromes. Yet the neurologic examination clearly showed that the cause had to lie elsewhere. The neurologist diagnosed an incomplete spinal cord transection syndrome at the T8 level. A sensory level (i.e., a band around the trunk below which multiple, or all, sensory modalities are impaired), spastic paraparesis with gait impairment, and bladder dysfunction are all typical findings of an incomplete spinal cord transection syndrome.
The slow progression of the deficits led the neurologist to suspect a slowly growing, and therefore probably benign, tumor compressing the spinal cord. The magnetic resonance imaging (MRI) scan that she ordered revealed the tumor, which was then completely resected by a neurosurgeon. Within a few months, the patient’s deficits resolved completely.
Diseases of the spinal cord have manifestations in the limbs and trunk and sometimes affect micturition, defecation, and sexual function. Their symptoms and signs depend on the level of the lesion and the affected structures—conducting pathways, anterior horn cells, or the entire cross-sectional extent of the spinal cord.
The spinal cord is the component of the central nervous system (CNS) that connects the brain to the peripheral nerves; its anterior horn cells, though located in the CNS, are functionally a part of the peripheral nervous system. The spinal cord contains the following:
In the white matter, fiber pathways leading from the brain to the periphery and vice versa.
In the gray matter, an intrinsic neuronal system consisting of:
Interneurons, that is, relay neurons for the conducting pathways and reflex loops.
Motor neurons in the anterior horns.
Autonomic neurons in the lateral horns.
The somatosensory neurons are located outside the spinal cord, in the spinal ganglia.
The topographic relations of the spinal cord, vertebral column, and nerve roots are shown in ▶ Fig. 7.1, and the major ascending and descending pathways of the spinal cord are shown in ▶ Fig. 7.2. The blood supply of the spinal cord is described later.
Fig. 7.1 Topographic relations of the vertebral column and nerve roots to the spinal cord. The growth of the spinal cord during embryonic development lags behind that of the spinal column; therefore, more caudally lying nerve roots traverse greater distances in the spinal subarachnoid space to reach their exit foramina. In the conventional numbering system, the cervical spinal nerves exit the spinal canal above the correspondingly numbered vertebra, while all spinal nerves from T1 downward exit below the correspondingly numbered vertebra. The conus medullaris generally ends at the upper L1 vertebral level but can also end more caudally, sometimes as far down as L3.
7.1.2 The Main Spinal Cord Syndromes and Their Anatomic Localization
The clinical manifestations of spinal cord lesions depend on their level and extent. Thus, the first step in diagnostic evaluation is topographic localization, that is, the deduction of the level and extent of the lesion from the patient’s constellation of neurologic deficits. The next step is the determination of the etiology, usually based on further criteria (accompanying nonneurologic manifestations, temporal course, findings of ancillary tests).
Spinal Cord Transection Syndrome
Spinal cord transection syndrome is the pattern of neurologic deficits resulting from damage of the entire cross-section of the spinal cord at some level. In an incomplete spinal cord transection syndrome, only part of the cord is damaged.
Most acutely arising cases of spinal cord transection syndrome are of either traumatic or ischemic origin; rare cases are due to inflammation or infection (transverse myelitis) or nontraumatic compression (e.g., by a hematoma or tumor).
The clinical features of the spinal cord transection syndrome are:
Dysfunction of all of the ascending sensory pathways up to the level of the lesion, and of the posterior horns and posterior roots at the level of the lesion: there is a sensory level below which all sensory modalities of sensation are impaired or absent.
Bilateral pyramidal tract dysfunction: spastic paraparesis or paraplegia, or, with cervical lesions, spastic quadriparesis or quadriplegia (immediately after a trauma, in the phase of “spinal shock” [diaschisis], there is usually flaccid weakness, which subsequently becomes spastic).
Dysfunction of the motor neurons of the anterior horn at the level of the lesion: possibly, flaccid paresis in the myotome(s) supplied by the cord at the level of the lesion, corresponding loss of reflexes and, later, muscle atrophy.
Partial and incomplete transection syndromes are more common than complete transection syndrome.
To understand the pathogenesis of spinal cord syndromes, one needs to know the anatomic course of the pyramidal tract (cf. ▶ Fig. 5.1) and of the sensory afferent pathways (the posterior columns and lateral spinothalamic tract, cf. ▶ Fig. 5.2). Only the essential structures for clinical purposes are shown in ▶ Fig. 7.2.
Fig. 7.2 Major fiber tracts of the spinal cord and the consequences of hemisection. a Clinically important structures are shown in cross-section, with color-coded descriptions of function. b The course of the nerve fibers and pathways, superimposed on a cross-sectional image. c The course of the somatosensory fibers and pathways in a coronal longitudinal section from the posterior root to the cortex. d Diagram of Brown-Séquard syndrome caused by hemisection of the spinal cord on the right side at one level. Strength, sensation to touch, position sense, and vibration sense are impaired ipsilaterally from the level of the lesion downward; pain and temperature sensation are impaired bilaterally at the level of the lesion and contralaterally below it.
As the pyramidal tract descends, it crosses in the medulla and then travels down the anterolateral column of the spinal cord. A lesion of the pyramidal tract in the spinal cord causes ipsilateral paresis.
The somatosensory afferent fibers in the posterior columns ascend ipsilaterally and terminate in the nucleus gracilis and nucleus cuneatus of the medulla. A lesion of the posterior columns thus impairs fine sensation (touch, stereognosis), proprioception, and vibration sense ipsilaterally ( ▶ Fig. 7.2).
Nociceptive fibers from the periphery enter the spinal cord through the dorsal roots, cross to the other side on the same segmental level in the anterior commissure of the spinal cord, and then ascend in the lateral spinothalamic tract ( ▶ Fig. 7.2). A lesion impairs pain and temperature sensation contralaterally.
See also the overview of the anatomic basis of sensory and motor function in Chapter ▶ 5.
Hemisection Syndrome (Brown-Séquard Syndrome)
The symptoms and signs of spinal cord hemisection are described in ▶ Table 7.1 (see also ▶ Fig. 7.2b). An anatomic or functional disconnection of one half of the spinal cord exactly to the midline is a rare event. Incomplete unilateral lesions present with a subset of these manifestations; the most common type of unilateral lesion preferentially affects the anterolateral column.
Vasomotor fibers of the lateral columns
Initially, warmth and redness of the skin; sometimes absence of sweating
Loss of proprioception and vibration sense, finely localized sensation of touch and pressure, two-point discrimination
Anterior horns and anterior roots
Segmental muscular atrophy and flaccid weakness
Entering posterior roots
Segmental anesthesia and analgesia
Lateral spinothalamic tract
Contralateral diminution or loss of pain and temperature sensation (dissociated sensory deficit)
Central Cord Syndrome
Central cord syndrome reflects damage to the decussating nociceptive fibers in the anterior commissure of the spinal cord (second neuron of the lateral spinothalamic tract). A dissociated sensory deficit is found in the corresponding segment(s).
Central cord syndrome is the classic presentation of syringomyelia (see ▶ Fig. 7.11) but can also be due to an intramedullary hemorrhage or tumor. Its clinical features are:
Pyramidal tract dysfunction: spasticity of the limbs below the level of the lesion; cervical lesions tend to affect the upper limbs more than the lower limbs.
Interruption of the pain and temperature fibers of the anterior spinal commissure: bilateral impairment of pain and temperature sensation at the level of the lesion, with preservation of touch (segmentally restricted dissociated sensory deficit); in analogous fashion, concomitant involvement of the posterior horn(s), if present, causes segmental impairment of touch sensation, either uni- or bilaterally, depending on whether one or both posterior horns are affected.
Dysfunction of the lateral horn/intermediolateral tract: autonomic and trophic disturbances (disturbances of sweating, nail growth, and bone metabolism; hyperkeratosis and edema; all disturbances more pronounced in the upper limbs).
Possible concomitant involvement of the spinothalamic tracts: (bilateral) deficit of pain and temperature sensation below the level of the lesion, with intact touch sensation.
Possible concomitant involvement of the motor neurons of the anterior horns at the level of the lesion: segmental flaccid weakness, loss of reflexes, and muscle atrophy.
Sparing of the posterior horns and spinocerebellar tracts: touch, vibration sense, and proprioception usually remain intact.
Bilateral Lesion of the Anterolateral Region of the Spinal Cord
In this situation, the posterior columns are intact, and there is thus no impairment of sensation to touch, proprioception, or vibration sense.
The most common cause is ischemia or infarction in the territory of the anterior spinal artery (see section ▶ 7.4.2).
Pyramidal tract dysfunction: depending on the level of the lesion, spastic quadriparesis (quadriplegia) or paraparesis (paraplegia), with enhanced intrinsic muscle reflexes and pyramidal tract signs.
Involvement of the spinothalamic tracts and the pain and temperature fibers crossing in the anterior spinal commissure: dissociated sensory deficit in the entire region of the body at and below the level of the lesion; less commonly, the spinothalamic tracts are spared and there is a segmentally restricted dissociated sensory deficit.
Intact posterior columns: no impairment of touch or proprioception.
Lesions of Both Posterior Columns
Sensations to touch, proprioception, and vibration sense are impaired, but the anterolateral columns are intact and there is thus no deficit of muscle strength or of pain and temperature sensation. The patient’s stance and gait are markedly ataxic.
A typical example is funicular myelosis due to vitamin B12 deficiency (see ▶ 22.214.171.124).
Below the lesion, impaired proprioception, vibration sense, fine touch and pressure sensation, and two-point discrimination.
Sensory ataxia that worsens in the dark or when the patient’s eyes are closed; positive Romberg test.
Sometimes, the is present (see section ▶ 8.2).
Isolated or Combined Long Tract Processes
In these situations, only some of the ascending or descending long tracts (or a single one) are affected.
The clinical syndromes vary correspondingly and include:
Pure spastic paraparesis (isolated lesion of the pyramidal tracts, e.g., in spastic spinal paralysis).
Impaired touch and position sense (posterior column lesion).
Ataxia (lesion of the spinocerebellar tracts and/or posterior columns).
Combinations of the above (e.g., pyramidal tract and posterior column dysfunction in funicular myelosis, dysfunction of these tracts and the spinocerebellar tracts in Friedreich ataxia).
Anterior Horn Lesions
Isolated involvement of the motor anterior horn cells causes weakness and atrophy without any sensory deficit.
This group of diseases includes spinal muscular atrophy and acute poliomyelitis and is characterized by:
Flaccid weakness of various muscles and muscle atrophy (as well as fasciculations in chronic processes).
Diminution or loss or reflexes.
No sensory impairment or bladder dysfunction.
Combined Anterior Horn and Long Tract Lesions
For example, muscle atrophy may be combined with pyramidal tract dysfunction.
This type of problem is seen, for example, in amyotrophic lateral sclerosis (ALS; see section ▶ 7.7.3), with simultaneous involvement of the anterior horn ganglion cells and of the pyramidal and corticobulbar tracts due to upper motor neuron degeneration. The patient has weakness, muscle atrophy, and fasciculations, but also brisk reflexes.
This syndrome affects the segment of the spinal cord above the conus medullaris, that is, levels T11 and/or T12.
Sacral and (sometimes) lumbar spinal functional deficits are seen, including:
Weakness of the muscles supplied by the affected lumbar and sacral segments.
Partial or total sensory loss in the affected lumbar and sacral dermatomes.
Usually, diminished lower limb reflexes (because the lesion destroys the sensory arm of the reflex loop as well as its motor arm); the Babinski sign is usually absent.
Bowel dysfunction, sphincter weakness.
Epiconus syndrome is clinically indistinguishable from cauda equina syndrome ( ▶ Fig. 7.3).
Fig. 7.3 Neurologic deficits resulting from spinal cord transection at various levels. Regarding the position of the conus medullaris, cf. legend to ▶ Fig. 7.1. a lesion at C7; b lesion at T10.
c epiconus syndrome and cauda equina syndrome, d conus medullaris syndrome.
Conus Medullaris Syndrome
The conus medullaris is the lower end of the spinal cord and lies in the spinal canal at the L1 level ( ▶ Fig. 7.3).
An isolated conus lesion typically produces:
Bowel dysfunction with sphincter weakness.
Possibly a dissociated sensory deficit or complete loss of sensation in the cutaneous distribution of the sacral and coccygeal spinal cord segments (saddle anesthesia).
usually, intact motor function and absence of pyramidal tract signs.
Cauda Equina Syndrome
Cauda equina syndrome ( ▶ Fig. 7.3) results from compression of the nerve roots coursing through the spinal canal below the conus medullaris, that is, below the L1 level. Unlike conus medullaris syndrome, it involves a variably severe impairment of sensory and motor function in the lower limbs (see also Radicular Syndromes, section ▶ 13.1).
Its clinical manifestations are:
Flaccid weakness and areflexia of the lower limbs, without pyramidal tract signs.
Impairment of all sensory modalities in multiple lumbar and/or sacral dermatomes, usually most pronounced in the “saddle” area.
Impaired urination, defecation, and sexual function, with sphincter weakness.
An epiconus lesion can present with the same signs and symptoms as the cauda equina syndrome.
A complete cauda equina syndrome can arise as the result of massive posteromedial intervertebral disk herniation ( ▶ Fig. 7.4). This condition demands immediate surgical treatment.
Fig. 7.4 Massive L4/L5 disk herniation causing acute cauda equina syndrome.
7.1.3 Further Diagnostic Evaluation of Spinal Cord Lesions
The further diagnostic evaluation of spinal cord lesions involves imaging studies (MRI, sometimes computed tomography [CT]) and laboratory testing of the cerebrospinal fluid (CSF) and blood. Electrophysiologic studies may also help determine the etiology. For details, see Chapter ▶ 4.
7.2 Spinal Cord Trauma
Traumatic spinal cord lesions are usually due to fractures and dislocations of the spine causing displacement of fragments of bone and/or intervertebral disk. The spinal cord can also be compressed by a traumatic hemorrhage in the spinal canal or sustain a direct traumatic contusion in the absence of a fracture. Spinal cord trauma is often a component of polytrauma.
The signs and symptoms of spinal cord trauma depend on the level and severity of the lesion, as shown schematically in ▶ Fig. 7.3.
Like traumatic brain injury, spinal cord trauma can be classified by severity:
Spinal concussion Immediately after blunt trauma to the spine, a more or less complete spinal cord transection syndrome arises, usually at a cervical or thoracic level. The neurologic deficits regress completely within minutes.
Spinal contusion The traumatic event has caused extensive structural damage and contusion of the spinal cord, usually with hemorrhage. There is a partial or complete spinal cord transection syndrome (depending on the extent of the lesion), including bladder dysfunction (see section ▶ 7.1.2) and an initially flaccid paraparesis (paraplegia) or quadriparesis (quadriplegia) (phase of spinal shock, also called diaschisis). The transection syndrome usually improves no more than partially, if at all.
Sometimes the level of a high spinal cord lesion can be inferred from visual inspection of the patient alone ( ▶ Fig. 7.5).
Fig. 7.5 A patient with a traumatic spinal cord lesion at the C7 level. The nerve supply to the elbow flexors, derived from the C6 root, is still intact; the triceps muscles, supplied by C7, are weak, as are the extensors of the wrist and finger joints.
Spinal shock in the acute phase of severe spinal cord trauma: motor, sensory, and autonomic function are lost below the level of the lesion, and the muscle tone (including that of the bladder) is flaccid.
Function may (partially) return after a few days or weeks. The initially flaccid paresis becomes progressively spastic.
Spinal cord compression In traumatic spinal fractures and dislocations, the spinal cord can be compressed by fragments of bone or intervertebral disk, or by hemorrhage within the spinal canal. Compression can also be partly or even entirely due to enlargement of the cord from within by edema or hemorrhage in a severe contusion. As long as the acute spinal cord compression is not severe enough to choke off the cord’s blood supply and cause infarction, the neural tissue may be able to recover its function again once the external compressing elements have been surgically removed, the traumatic spinal cord edema has subsided, and any hemorrhage within the cord has been resorbed.
Practical steps In acute spinal cord trauma, these include the following:
Keep the airway free (to permit breathing and prevent aspiration), stabilize and monitor circulatory function, stop any ongoing hemorrhage.
Safely transport the patient to a trauma center (e.g., hard collar, back board, vacuum mattress).
Perform a gentle, nontraumatic neurologic examination to determine the level of the lesion.
Order targeted neuroimaging studies, usually CT possibly followed by MRI, to identify spinal fractures and dislocations of the vertebral column and assess damage of the intraspinal structures, including the spinal cord; objectively correlate the image findings with the clinically determined level, extent, and type of spinal cord injury.
Insert a bladder catheter.
Surgically decompress the spinal cord if indicated, in case of bony lesions, hematomas, etc.
Prevent decubitus ulcers from the beginning, with frequent repositioning of the patient.
High-dose steroids (given routinely in the past) are currently not recommended, as recent studies suggest that their complications may outweigh their modest benefit.
Patients should be transferred as soon as possible to a rehabilitation hospital specializing in spinal cord trauma where they can receive appropriate physiotherapy, ergotherapy, and psychological support.