, Joon Woo Lee1 and Jong Won Kwon2
(1)
Department of Radiology, Seoul National University Bundang Hospital, Seongnam, Kyonggi-do, Republic of Korea
(2)
Department of Radiology, Samsung Medical Center, Seoul, Republic of Korea
17.1 Idiopathic Spinal Cord Herniation
17.2 Hirayama Disease
17.3 Subacute Combined Degeneration
17.4 Radiation Myelitis
17.5 Spinal Visceral Larva Migrans of Toxocara canis
17.6 Conjoined Nerve Root
17.7 Guillain–Barré Syndrome
17.8 Hereditary Motor and Sensory Neuropathies (HMSN)
17.9 Illustrations: Rare but Characteristic Spinal Disorders: Neural
17.9.1 Idiopathic Spinal Cord Herniation
17.9.2 Hirayama Disease
17.9.3 Subacute Combined Degeneration
17.9.4 Radiation Myelitis
17.9.5 Spinal Visceral Lava Migrans of Toxocara canis
17.9.6 Conjoined Nerve Root
17.9.7 Guillain–Barré Syndrome
17.9.8 Hereditary Motor and Sensory Neuropathies
References
Abstract
This chapter will discuss rare spinal disorders which have characteristic imaging findings and mainly involve spinal cord or nerve roots. These include idiopathic spinal cord herniation, Hirayama disease, subacute combined degeneration, radiation myelitis, spinal visceral larva migrans of Toxocara canis, conjoined nerve root, Guillain–Barré syndrome, and hereditary motor and sensory neuropathies.
This chapter will discuss rare spinal disorders which have characteristic imaging findings and mainly involve spinal cord or nerve roots. These include idiopathic spinal cord herniation, Hirayama disease, subacute combined degeneration, radiation myelitis, spinal visceral larva migrans of Toxocara canis, conjoined nerve root, Guillain–Barré syndrome, and hereditary motor and sensory neuropathies.
17.1 Idiopathic Spinal Cord HerniationIdiopathic spinal cord herniation is a disorder in which the spinal cord herniates through an anterior dural defect in the upper or middle thoracic level (Parmar et al. 2008). Idiopathic spinal cord herniation is an uncommon clinical entity resulting in progressive myelopathy. On sagittal MR images, an anterior kink of the thoracic spinal cord is seen with focal enlargement of the dorsal subarachnoid space, most commonly between the levels of the T4 and T7 vertebrae. On axial images, part of the spinal cord is seen outside the anterior dura, and the spinal cord appears elongated and rotated at the level of herniation. Sometimes, cerebrospinal fluid can leak into the anterior epidural space, manifest as a thin sliver of fluid signal in the anterior epidural space. In long-standing spinal cord herniation, there can also be bony erosion in the posterior vertebral body due to the herniated spinal cord. On CT myelography, similar findings (anterior kinking of spinal cord on sagittal images, anterior herniation of the spinal cord on axial images) are also evident. Common differential diagnoses include intradural arachnoid cyst, spinal cord adhesion, and arachnoid web with spinal cord deformity. The key to diagnosing spinal cord herniation is to detect the anteriorly herniated spinal cord outside the dura margins on axial images.
17.2 Hirayama DiseaseHirayama disease (juvenile muscular atrophy of distal upper extremity) is a rare form of cervical myelopathy that affects predominantly males in their second and early third decades. Clinical features include muscular weakness and atrophy of the hand and forearm. Interestingly, the brachioradialis muscle is spared; thus the pattern of forearm involvement is referred to as an oblique amyotrophy. It is characterized by progressive muscular weakness and atrophy of the distal upper limbs, followed by spontaneous arrest within several years. Dynamic cord compression during neck flexion with forward displacement of the posterior dura is a characteristic finding. A possible etiology involves disproportional lengths between the vertebral column and the dural canal that may lead to a 「tight」 dural canal. The normal cervical dura is slack and consists of transverse folds during neck extension. With flexion, the length of the cervical canal increases. In normal patients, the dural slack compensates for the increased length of the cervical canal during flexion. Patients with Hirayama disease may have an imbalance in the growth of the vertebrae and dura resulting in a relatively short dural canal with less ability to compensate; thus the dural canal becomes tight with neck flexion. This results in anterior shift of the posterior dural wall causing spinal cord compression. The pathogenesis of cervical myelopathy may be due to ischemic changes or chronic trauma from repeated neck flexion. Chronic compression may cause microcirculatory disturbances in the anterior portion of the cord, leading to necrosis of the anterior horn cells. Changes are often worst at the C6 vertebral level primarily affecting the anterior horn cells, with cord atrophy developing in later stages of the disease. On MR, flexion sagittal images demonstrate forward displacement of the posterior dura. The posterior epidural space enlarges with flexion and is seen as a crescent of high T1 and T2 signal due to congestion of the posterior internal vertebral venous plexus. On contrast-enhanced images, uniform enhancement of the epidural space with flow voids is seen. On axial images, asymmetric flattening of the spinal cord with forward shifting of the posterior dura can be observed. One article has described loss of attachment of more than two-thirds between the posterior dura and adjacent lamina at the lower cervical level as a reliable imaging finding suggestive of Hirayama disease on MRI performed in the neural position (Chen et al. 2004).
17.3 Subacute Combined DegenerationThe clinical manifestations of vitamin B12 deficiency include hematologic abnormalities such as megaloblastic anemia, while neurologic abnormalities caused by its effect on the brain, peripheral and optic nerves, as well as posterior and lateral columns of the spinal cord are known collectively as subacute combined degeneration (SCD). The most frequent clinical manifestation of vitamin B12 deficiency is SCD of the spinal cord, although it is in itself an uncommon cause of myelopathy (Ravina et al. 2000). The clinical findings of SCD include insidious subacute onset of weakness, paresthesia, loss of vibratory sensation, and sensory ataxia. Symptoms are usually symmetric and progress from distally to proximally and may progress to paraplegia in untreated cases. Timely diagnosis and appropriate treatment is important to prevent irreversible neurologic injury. Vitamin B12 cobalamin is a complex molecule found in food from animal and some plant sources. Following ingestion, vitamin B12 is bound to intrinsic factor (IF) secreted by gastric parietal cells; the B12–IF complex then binds to the mucosa of the terminal ileum where B12 is absorbed. Any abnormality along this pathway may lead to vitamin V12 deficiency. However, because of substantial total body stores of 2–5 mg, the effects of vitamin B12 deficiency from malabsorption syndromes such as pernicious anemia, regional enteritis, tropical sprue, celiac disease; surgical procedures such as gastrectomy and ileal resection; as well as inadequate intake in strict vegetarians may not develop for several years.
The cause of vitamin B12-associated neurologic disease is consequent to increased myelinolytic tumor necrosis factor-α (TNF-α) and decreased neurotrophic factor levels. Vitamin B12 deficiency leads to an overproduction of TNF-α and downregulation of two neurotrophic factors: epidermal growth factor (EGF) and interleukin-6 (Scalabrino et al. 2004). Vitamin B12-associated myelopathy is histologically characterized by multifocal demyelination, vacuolization, and axonal degeneration typically involving the dorsal and lateral columns and occasionally the ventral column (Timms et al. 1993). Linear T2 hyperintensities appearing as an 「inverted V」 in the posterior column of the spinal cord is a characteristic finding on MR (Timms et al. 1993). In some patients, bilateral paired nodular T2 hyperintensities described as 「dumbbell」- or 「binocular」-shaped areas are seen.
17.4 Radiation MyelitisRadiation can be a cause of myelopathy (Calabro and Jinkins 2000). On MR images, radiation myelitis shows similar features to other non-tumorous myelopathy such as acute transverse myelitis or multiple sclerosis. These features include patchy T2 hyperintensities and patchy enhancement within the spinal cord. The clue that points to radiation myelitis as a cause is a history of previous radiation therapy to the involved segment. Fatty marrow signal change in the vertebral bodies at the same region is also sometimes observed. In the acute phase of radiation myelitis, the spinal cord is enlarged and demonstrates T1 hypointensity and T2 hyperintensity. Contrast enhancement is variable and may be patchy or ringlike. In the chronic phase, the affected portions can become atrophic.
17.5 Spinal Visceral Larva Migrans of Toxocara canisHumans are manifested by Toxocara canis as visceral larva migrans when uncooked cow or cattle liver or meat containing the infective form of Toxocara canis is ingested. Spinal visceral larva migrans of Toxocara canis is an unusual cause of non-tumorous myelopathy. Myelopathy is secondary to hematogenous infestation of the spinal cord with visceral larva migrans. There may be migration from pulmonary lesions. Typical MR findings of spinal visceral larva migrans are single lesion, short segmental involvement of T2 hyperintensity with mild cord swelling, and focal nodular enhancement on posterior or posterolateral columns after gadolinium administration (Lee et al. 2010). The diagnosis of toxocariasis relies on high titers of Toxocara canis antibodies, eosinophilia in blood and/or cerebrospinal fluid, and demonstration of an intrathecal synthesis of anti-Toxocara canis antibodies. The clinical and radiologic improvement as well as the normalization of the cerebrospinal fluid parameters after anti-helminthic therapy supports the diagnosis (Xinou et al. 2003).
17.6 Conjoined Nerve RootA conjoined nerve root is composed of two adjacent nerve roots which share a common dural envelope at some point along their course from the dural sac. The prevalence of lumbosacral nerve root anomalies varies widely. Myelography reports of patients complaining of leg pain and suspected disk herniation reveal an incidence of suspected nerve root anomalies in 4 % (Kadish and Simmons 1984). Anatomic studies have demonstrated a much higher incidence (Kikuchi et al. 1984).
Conjoined nerve roots are commonly found between L5–S1 and S1–2 (Song et al. 2008). Conjoined nerve root may be divided into various types. The most clinically relevant pattern is one where the common nerve root outside the dura bifurcates into an upper nerve coursing in a horizontal direction occupying the lower part of the neural foramen and a lower nerve coursing in a more vertical direction just posterior to the upper nerve in the epidural space. In such a pattern, the upper nerve can be easily compressed by a mild disk bulge and mild facet arthropathy due to its horizontal course. The lower nerve can be also compressed by the facet joint along its vertical course. If the presence of a conjoined nerve root is not discovered before operation, the nerve root may be injured during retraction of the dural sac or could even be mistaken for a herniated disk and resected. We suggest three radiologic signs on axial MR images at the disk level useful for diagnosing conjoined nerve roots preoperatively: these are as follows: (1) corner sign, asymmetric morphology of the anterolateral corner of the dural sac; (2) fat crescent sign, intervening extradural fat tissue between the asymmetric dural sac and conjoined nerve root; and (3) parallel sign, visualization of the parallel course of the entire nerve root at the disk level (Song et al. 2008).
17.7 Guillain–Barré SyndromeGuillain–Barré syndrome is a relatively common acute, and rapidly progressive, inflammatory demyelinating polyneuropathy. On contrast-enhanced MR, there is marked enhancement of the thickened nerve roots at the conus medullaris and of the cauda equina. The enhancement can be confined to the anterior roots or involve the anterior and posterior nerve roots (Byun et al. 1998; Berciano 1999; Georgy et al. 1994; Iwata and Utsumi 1997). The spinal cord and nerve roots in the thecal sac normally do not enhance because of the blood–nerve and blood–brain barriers. Other causes of intradural nerve root enhancement are leptomeningeal metastases, lymphoma, chronic inflammatory demyelinating polyneuropathy (CIDP), sarcoidosis, AIDS-related cytomegalovirus polyradiculopathy, Lyme disease, and postoperative arachnoiditis. Diffuse enhancement of intradural nerve roots with a history of acute progressive ascending and symmetric paralysis of the extremities strongly suggest Guillain–Barré syndrome.
17.8 Hereditary Motor and Sensory Neuropathies (HMSN)Hereditary motor and sensory neuropathies (HMSN) are a heterogeneous group of genetically determined peripheral neuropathies characterized by symmetrical and predominately distal motor and sensory disturbances and a slowly progressive course.
HMSN is classified into three types: HMSN type 1 (Charcot–Marie–Tooth, CMT type 1), HMSN type 2 (CMT type 2), HMSN type 3 (Dejerine–Sottas disease, DSD). CMT type I and DSD are the disorders most characteristically associated with marked thickening of peripheral nerves (hypertrophic neuropathies).
Charcot–Marie–Tooth (CMT) disease is the most common inherited neuromuscular disorder. CMT disease can be further divided into two types based on the electrophysiological and pathological findings. CMT disease type 1 is the demyelinating form and is characterized by a slow motor median nerve conduction velocity. CMT disease type 2 is the axonal form and shows a normal or slightly reduced nerve conduction velocity (Gaeta et al. 2012).
On spine MR, diffuse thickening of the intradural nerve roots and extradural spinal nerves is a characteristic finding suggestive of HMSN. On postcontrast images, the intradural nerve roots can be enhanced in HMSN (Cellerini et al. 2000). Diffuse hypertrophy of the cauda equine and spinal nerves are also seen in chronic inflammatory demyelinating polyneuropathy (CIDP) (Vallat et al. 2010). The differentiation between HMSN and CIDP is difficult by MRI findings only.
Forget Me Nots!
Possible causes for anterior kinking of thoracic spinal cord include spinal cord herniation, intradural arachnoid cyst, spinal cord adhesion, and arachnoid web.
Dynamic cord compression during neck flexion with forward displacement of the posterior dura is a characteristic finding of Hirayama disease.
Linear T2 hyperintensities appearing as an 「inverted V」 in the posterior column of the spinal cord are a characteristic finding of subacute combined degeneration.
MR findings of spinal visceral larva migrans of Toxocara canis are short segmental T2 hyperintensity of spinal cord, mild cord swelling, and focal nodular enhancement on posterior or posterolateral columns after gadolinium administration.
Diffuse enhancement of intradural nerve roots with a history of acute progressive ascending and symmetric paralysis of the extremities strongly suggest Guillain–Barré syndrome.
17.9 Illustrations: Rare but Characteristic Spinal Disorders: NeuralFig. 17.1
Idiopathic spinal cord herniation. Idiopathic spinal cord herniation is a disorder in which the spinal cord herniates through an anterior dural defect in the upper or middle thoracic level. Idiopathic spinal cord herniation is an uncommon clinical entity causing progressive myelopathy. On the sagittal schematic illustration (a) and CT myelography (b), an anterior kink of the thoracic spinal cord (arrow) is seen with enlargement of the dorsal subarachnoid space; this most commonly occurs between the levels of T4 and T7. On axial images (c, d) part of the spinal cord (dotted arrow) is seen outside the anterior dura; the spinal cord is elongated and rotated at the level of herniation. Cerebrospinal fluid can sometimes leak into the anterior epidural space, visible as fluid signal in the anterior epidural space. In long-standing spinal cord herniation, there can also be bony erosions in the posterior vertebral body due to the herniated spinal cord. Common differential diagnoses include an intradural arachnoid cyst, spinal cord adhesion, and arachnoid web with spinal cord deformity. The clue to identifying spinal cord herniation is to find the anteriorly herniated spinal cord outside the dura on axial images
Fig. 17.2
Spinal cord herniation in a 68-year-old man. On sagittal MR T2-weighted images (a, b), an anterior kink of the thoracic spinal cord (arrow) is seen with enlargement of the dorsal subarachnoid space; this is most commonly found between the levels of T4 and T7. On axial T2-weighted (c) and T1-weighted images (d) part of the spinal cord is seen outside the anterior dura (dotted arrow); the spinal cord is elongated and rotated at the level of herniation. Cerebrospinal fluid can leak into the anterior epidural space, visible as fluid signal (arrowheads) in the anterior epidural space. On CT myelography (e) an elongated and rotated spinal cord with anterior kinking is seen without an abnormal intradural filling defect
Fig. 17.3
Idiopathic spinal cord herniation in a 59-year-old woman. On sagittal MR image (a), an anterior kink of the thoracic spinal cord is seen with enlargement of the dorsal subarachnoid space (arrow). On axial T2-weighted (b) and T1-weighted images (c) part of the spinal cord is seen outside the anterior dura; the spinal cord is elongated and rotated at the level of herniation (dotted arrows)
Fig. 17.4
Idiopathic spinal cord herniation with CSF leakage into the anterior epidural space in a 61-year-old man. On the sagittal T2-weighted image, an anterior kink of the thoracic spinal cord (arrow) is evident with enlargement of the dorsal subarachnoid space. Cerebrospinal fluid can leak into the anterior epidural space, visible as fluid signal in the anterior epidural space (arrowheads)
17.9.2 Hirayama DiseaseFig. 17.5
Hirayama disease in a 16-year-old man. The posterior epidural space enlarges with flexion (arrow) and is seen as a crescent of high signal on T2-weighted images (a) due to congestion of the posterior internal vertebral venous plexus. On postcontrast images (b), uniform enhancement of the epidural space with flow voids (dotted arrow) is seen
Fig. 17.6
Hirayama disease in a 16-year-old man. Loss of attachment (dotted arrows) between the posterior dura and adjacent lamina at the lower cervical level on the gradient echo axial image (a) can be a reliable finding suggestive of Hirayama disease. On the flexion T2-weighted image (b), there is anterior displacement of the posterior dura (arrows) with a widened posterior epidural space
17.9.3 Subacute Combined DegenerationFig. 17.7
Subacute combined degeneration in a 41-year-old man with schematic figure (a) and T2-weighted image (b). On the axial T2-weighted image (b), there is linear T2 hyperintensity with an 「inverted V」 appearance (arrows) in the posterior column of the spinal cord, suggestive of subacute combined degeneration
Fig. 17.8
Subacute combined degeneration in a 64-year-old man. On the axial T2-weighted image (a), there is linear hyperintensity (dotted arrows) with an 「inverted V」 appearance in the posterior column of the spinal cord, suggestive of subacute combined degeneration. On the sagittal T2-weighted image (b), a linear band-like hyperintensity (arrows) is seen in the posterior spinal cord from C4 to C6
Fig. 17.9
Subacute combined degeneration in a 71-year-old man. In some patients, bilateral paired nodular T2 hyperintensities with a 「dumbbell」 or 「binocular」 appearance (dotted arrows) are seen in the posterior column, as is in this case on the T2-weighted axial image (a). On the T2-weighted sagittal image (b), a linear band-like hyperintensity (arrows) is seen in the posterior spinal cord
17.9.4 Radiation MyelitisFig. 17.10
Radiation myelitis in a 28-year-old man. On the T2-weighted sagittal image (a), patchy high signal change (arrow) is seen in the spinal cord from C2 to C4. On the T1 inversion recovery sagittal image (b), the lesion shows low signal intensity (arrow). On axial images, there is patchy T2 hyperintensity (arrow, c) and enhancement (arrow, d) in the right side of the spinal cord posteriorly. These features are similar to other non-tumorous myelopathy such as acute transverse myelitis or multiple sclerosis. The clue pointing to radiation myelitis as the etiology is a history of radiation to the area and post-radiation changes involving the adjacent vertebral bodies (fatty marrow change)
Fig. 17.11
Radiation myelitis in a 55-year-old man. The patient developed slow, insidious onset of paresthesia on trunk and weakness of left leg 3 years after neck radiation therapy for nasopharyngeal cancer. T1-weighted sagittal image (a) of cervicothoracic spine shows diffuse increased signal intensity throughout all cervical and upper thoracic vertebral bodies with clear caudal demarcation corresponding to radiotherapy portal and nonspecific enlargement of the spinal cord. T2-weighted sagittal image (b) shows long segment region of abnormal hyperintensity within the cervical spinal cord. T2-weighted axial image (c) shows ill-defined signal elevation in the cervical cord. Postcontrast T1-weighted axial image (d) of same slice as figure (c) shows a necrotic center with enhancing rim within the left side of the cervical spinal cord. In the acute phase of radiation myelitis, the spinal cord is enlarged and demonstrates T1 hypointensity and T2 hyperintensity. Contrast enhancement is variable and may be patchy or ringlike. In the chronic phase, the affected portions can become atrophic
Fig. 17.12
Radiation myelitis in a 19-year-old man who presented with weakness of both lower extremities after radiation therapy for mediastinal lymphoma 23 months ago. T2-weighted sagittal image (a) shows long segment region of hyperintensity within the cervicothoracic spinal cord. There is ill-defined low signal area in the middle portion of the T2 hyperintensity. Postcontrast T1-weighted image (b) shows spindle-shaped enhancement with central nonenhancing necrosis in upper thoracic cord. Open biopsy was done to rule out the possibility of recurrence of lymphoma at the enhancing region and the pathology revealed radiation change
17.9.5 Spinal Visceral Lava Migrans of Toxocara canisFig. 17.13
Spinal visceral lava migrans of Toxocara canis in a 41-year-old man. The patients had history of ingesting uncooked cow liver and meat frequently. T2-weighted sagittal image (a) shows patchy high signal intensity and swelling of cervical spinal cord at C5–6 level. There is no demarcated mass-like lesion or focal hypointensity within the cord, which suggests non-tumorous myelopathy. Fat-saturated postcontrast T1-weighted image (b) shows focal nodular enhancement (arrow) on the dorsal segment of the spinal cord at the level of C6. Single, focal nodular enhancing lesion on posterior or posterolateral segment of the spinal cord, relatively short segment of T2 hyperintensity, and migration of the lesion are characteristics of spinal visceral lava migrans of Toxocara canis
Fig. 17.14
Spinal visceral lava migrans of Toxocara canis in a 44-year-old man. The patient had history of ingesting raw cow liver. T2-weighted sagittal image (a) of thoracic spine shows intramedullary segmental homogeneous hyperintensity of T9–T12 levels. Fat-saturated postcontrast T1-weighted sagittal image (b) and axial image (c) shows focal nodular enhancement (arrow) on posterior segment within the cord at T11 level. Coronal chest CT (d) of the same patient shows multiple ground-glass opacities with peripheral halo in the both lungs, representing pulmonary eosinophilic infiltration. The patient had pulmonary and spinal visceral lava migrans of the Toxocara canis
17.9.6 Conjoined Nerve RootFig. 17.15
Schematic illustration of the MR signs of conjoined nerve roots (a, b). Schematic diagram depicting a change in the dural sac corner (asymmetric morphology of the anterolateral corner of the dural sac, 「corner sign」), intervening extradural fat tissue between the asymmetric dural sac and the conjoined nerve root (「fat crescent sign」) and visualization of the parallel course of the entire nerve root at the disc level (「parallel sign」)
Fig. 17.16
Conjoined nerve root of the right L5 and S1 nerve roots in a 37-year-old woman. Horizontal direction of the right L5 nerve root (arrow) and vertical direction of the right S1 nerve root (dotted arrow) after division in the epidural space from the common trunk is seen on T1-weighted axial images. The right corner of the dural sac shows asymmetric morphology (「corner sign」). The entire L5 nerve root is seen on a single axial plane at the disk level (「parallel sign」). The upper nerve can be easily compressed by a mild disk bulge and mild facet arthropathy due to its horizontal course. The lower nerve can be also compressed by the facet joint along its vertical course. If the presence of a conjoined nerve root is not discovered before operation, the nerve root may be injured during retraction of the dural sac or could even be mistaken for a herniated disk and resected
Fig. 17.17
Conjoined nerve root of the left L5 and left S1 nerve roots in a 52-year-old woman. Horizontal direction of the left L5 nerve root (arrow) and vertical direction of the left S1 nerve root (dotted arrow) from the common trunk (open arrows) in the epidural space are seen in T2-weighted sagittal images (a, b) and T1-weighted axial images (c, e)
17.9.7 Guillain–Barré SyndromeFig. 17.18
Guillain–Barré syndrome in a 56-year-old woman shown on postcontrast sagittal (a) and axial (b) images. Enhancement of the anterior rootlets within the dura sac (arrows) is a characteristic finding of Guillain–Barré syndrome. The enhancement can be confined to the anterior rootlets or can involve both the anterior and posterior nerve roots
Fig. 17.19
Guillain–Barré syndrome in a 55-year-old woman shown on postcontrast sagittal (a) and axial (b, c) images. Enhancement of the anterior rootlets (arrows) within the dural sac is a characteristic finding of Guillain–Barré syndrome
Fig. 17.20
Guillain–Barré syndrome in a 4-year-old boy shown on postcontrast axial (a, b) and sagittal (c) images. Diffuse enhancement of the cauda equina is observed. Intradural nerve roots do not enhance normally. In Guillain–Barré syndrome, the enhancement can be confined to the anterior roots or can affect both anterior and posterior nerve roots
17.9.8 Hereditary Motor and Sensory NeuropathiesFig. 17.21
Charcot–Marie–Tooth disease type 1 in a 22-year-old woman with progressive lower leg weakness and gait disturbance since 2 years ago. Electrophysiologic study was compatible with generalized peripheral polyneuropathy (uneven nonuniform demyelination). Charcot–Marie–Tooth disease type 1 was diagnosed by detecting CPMP22 gene duplication. The intradural nerve roots are diffusely thickened in the lumbar spine (a–e). The nerve roots in the cervical spine and brachial plexus are also diffused thickened (f). Charcot–Marie–Tooth (CMT) disease is the most common inherited neuromuscular disorder. Hereditary motor and sensory neuropathies (HMSN) are a heterogeneous group of genetically determined peripheral neuropathies characterized by symmetrical and predominately distal motor and sensory disturbances and a slowly progressive course. HMSN is classified as three types: HMSN type 1 (CMT type 1), HMSN type 2 (CMT type 2), and HMSN type 3 (De´je`rine–Sottas disease, DSD). CMT type I and DSD are the disorders most characteristically associated with marked thickening of peripheral nerves (hypertrophic neuropathies). On spine MR, diffuse thickening of the intradural nerve roots and extradural spinal nerves is a characteristic finding suggestive of HMSN
Fig. 17.22
Hereditary motor and sensory neuropathies (HMSN) in a 51-year-old man. Brachial plexus are diffusely hypertrophied (a). Intradural and extradural nerve roots in the cervical spine are thickened and enhanced (b). Intradural nerve roots of cauda equina and spinal nerves in the lumbosacral plexus are also diffusely hypertrophied (c–e). The intradural and peripheral nerves are diffusely hypertrophied in HMSN (「hypertrophic neuropathies」)
References