Spinal Cord Anatomy and Function

• The study notes cover the introduction to Spinal Cord Injury (SCI) and Neuroanatomy.

Objectives for Understanding SCI

• Describe the differences and similarities between upper motor neuron (UMN) and lower motor neuron (LMN) spinal cord lesions.
• Describe the clinical presentation of common SCI syndromes.
• Recognize the signs and symptoms of autonomic dysreflexia (AD).
• Determine sensory and motor neurological levels in a patient with SCI (using the ASIA scale).
• Distinguish between bowel and bladder issues in UMN and LMN spinal cord lesions.

Key Steps in Understanding SCI

• Step 1 focuses on neuroanatomy, general considerations, and pathogenesis.
• Step 2 involves disease course, clinical findings, red flags, and diagnosis/differential diagnosis.
• Step 3 emphasizes medical management, prognosis, and clinical management.

Neuroanatomy Overview

• The central nervous system (CNS) includes UMNs, sensory components, and other areas like the basal ganglia and cerebellum.
• The peripheral nervous system (PNS) includes sensory and autonomic components, as well as LMNs.
• UMN components in the CNS include the cortical region, brainstem, and spinal cord.
• LMN components within the CNS start with the motor cranial nerve and nuclei then continue into the PNS.
• The PNS includes the anterior horn, spinal nerve root, peripheral nerve, and neuromuscular junction (NMJ) that connects to muscles.

General Considerations

• The spinal cord typically ends around the L1-L2 vertebral level, which is considered UMN.
• The conus medullaris is the tapered end of the spinal cord.
• The cauda equina comprises nerve roots extending below the spinal cord, around the L2 level and below, which are considered LMN.

UMN vs. LMN

• UMN lesions involve the lateral cortical spinal tract within the spinal cord.
• LMN lesions involve the anterior horn cell and spinal nerve root.

Spinal Cord Tracts

• Key tracts include the lateral corticospinal tract (responsible for voluntary movement), the anterior horn cell, and other sensory and motor pathways critical for function.

Spinal Cord Syndromes

• Recognized syndromes include lateral cord (Brown-Séquard), complete cord, central cord, anterior cord, posterior cord, pure motor, conus, and cauda equina syndromes.

Clinical Findings: UMN vs. LMN Lesions

• Initial spinal shock involves flaccid paralysis, loss of sensation, and motor function.
• Acute upper motor neuron lesions can initially present with decreased reflexes and tone.

Prevalence and Incidence of SCI

• SCI can drastically alter life in an instant, with 8,000-50,000 acute injuries each year in North America.
• Approximately 305,000 people are living with SCI in the U.S. as of 2023.
• The main causes of SCI are motor vehicle accidents (MVAs), falls, and violence.
• About 60% of injuries occur in children or young adults ≤ 30 years old.
• SCI is most common between ages 16-30.
• The mean age at injury is 42.0 years (2017).
• SCI affects men four times more than women (80.9%).

Etiology of Traumatic SCI

• Initial injury occurs through four mechanisms.
• Impact with persistent compression, like in a burst fracture.
• Impact with transient compression following hyperflexion/hyperextension injuries.
• Distraction caused by forcible stretching of the spinal cord or its blood supply.
• Laceration from missile injuries, sharp bone fragment dislocation, or severe distraction.

Pathogenesis

• Primary injury involves the loss of neurons/axons and demyelination.
• Secondary injury includes further loss of neurons/axons, demyelination, inflammation, reactive oxidative damage, astrocytic glial scar formation, and cyst formation.

Neuroinflammation and Recovery

• The microenvironment is critical for recovery.
• Inflammation at the lesion site is well-known, but effects at different levels are less understood.
• Inflammation can occur up to 10 segments away from the injury site.
• Reducing inflammation may improve recovery.
• Inflammation (specifically in the lumbar/sacral regions) can produce maladaptive neuroplasticity and hinder motor learning.

Disease Course

• SCI typically involves an acute onset, then progression to a stable state.
• It starts with an initial traumatic event, leading to spinal shock with flaccid paralysis and loss of sensation/motor function.
• Next is emergency response including immobilization and stabilization as well as diagnosis via MRI.
• The condition stabilizes with the possibility of UMN signs like spasticity and hyperreflexia.
• Next neurologic return: Most recovery occurs within one year, with the most rapid recovery in the first six months.

Diagnostic Studies

• MRI is the diagnostic tool of choice.
• Diagnostic studies also include X-rays, CT scans, EMG and NCV.

Medical Management

• Standard care include immobilization via halo or TLSO (avoiding prolonged immobilization), early intervention with closed reduction/spinal decompression, corticosteroids (early methylprednisolone IV bolus), BP management, general care, and nutritional support.
• experimental treaments include implanted spinal stimulators, locomotor training, nanofibers ("Dancing Molecules").

Prognosis

• Mortality post-SCI ranges from 4-17%.
• Predisposing factors include age, higher injury levels, pulmonary embolism, medical co-morbidities, and suicide.
• Brown-Séquard greatest potential for recovery (75-90% walk independently post DC/70%ADLs).
• Central cord syndrome: lower extremity (LE) recovery, bowel and bladder function seen early.
• Age: < 50: faster, more successful recovery.
• Also, ability to attain intensive locomotor training.

Rehab Issues in SCI

• Common issues include bladder dysfunction, bowel dysfunction, decubitus ulcers, autonomic dysfunction, sexual dysfunction, spasticity, and wheelchair seating/positioning.

Bowel and Bladder Dysfunction: UMN vs. LMN Lesions

• In UMN lesions (C1-L1), bowel function is hyperreflexic (spastic paralysis due to intact reflexes), and bladder function is spastic (overactive urinary bladder/sphincter).
• Conversely, in LMN lesions (L2-S5), bowel function is areflexic (flaccid paralysis with no muscle tone), and bladder function is areflexic (detrusor unable to contract).

Autonomic Dysreflexia (AD)

• It is an exaggerated, massive autonomic response to strong sensory stimuli.
• AD occurs due to a loss of inhibitory control of sympathetic neurons and typically occurs in lesions at T6 and above.
• Common causes include bladder/bowel distension, ulcers, constrictive clothing, and ingrown toenails
• Remove strong stimuli and monitor vitals - Medical emergency!

Symptoms of Autonomic Dysreflexia

• Symptoms include a pounding headache (caused by high BP), hypertension (BP > 200/100), diaphoresis above the level of injury, red blotches on the skin above the level of spinal injury, and cutis anserina (goosebumps). Additional signs are flushed face, nausea, slow pulse (<60 beats/minute), cold/clammy skin below the level of spinal injury, restlessness, and nasal congestion.

Male Sexual Dysfunction

• The autonomic nervous system is essential for penile erection.
• The parasympathetic nervous system initiates erectile response (S2-4).
• The sympathetic nervous system enables ejaculation (L1-3).
• Common issues include erectile dysfunction (ED), ejaculation difficulties, and fertility problems.
• Treatment options include surgical procedures (penile prosthesis), vacuum devices, and pharmacology.

Female Sexual Dysfunction

• The autonomic nervous system plays a crucial role.
• T11-L2 innervates the uterus.
• S1-S4 innervates the vulva and vagina.
• Common Issues include altered menstrual period, lubrication issues, and hormonal changes. Though Fertility is often unaffected.

Spasticity

• Characterized by a velocity dependent increase in tonic stretch reflexes with passive movement.
• UMN lesions above the cauda equina cause spasticity.
• Absent immediately post acute injury-develops over weeks.
• Treatment includes stretching/contracture management.
• Medications: Baclofen, Tizanidine, Diazepam, Dantrolene, and Clonodine can be used.
• Other options: Botox, Xeomin, phenol nerve blocks, and intrathecal baclofen pump may be considered.

ASIA Impairment Scale:

• Used, along with established protocols, to determine the neurological classification and extent of an SCI
• A: Complete, no motor or sensory function is preserved in the sacral segments S4-5
• B: Incomplete, sensory but not motor function is preserved below the neurological level and includes the sacral segments S4-5
• C: Incomplete, motor function is preserved below the neurological level, and more than half of the key muscles below the neurological level have a muscle grade of less than 3
• D: Incomplete, motor function is preserved below the neurological level, and at least half of the key muscles below the neurological level have a muscle grade of 3 or more.
• E: Normal, motor and sensory functions are normal

Determination:

• Sensory level - most caudal level with normal sensation for dermatomes. Right vs left side may differ
• Motor level- most caudal level of spinal nerve, may differ right vs left. Thoracic region motor level is presumed to be the same as the sensory level.
• Neurologic level, the most caudal segment of the cord where sensory and motor components are intact.

SCI Classification:

• Determine sensory levels on right and left sides.
• Determine motor levels on tight and left sides.
• Determine the neurological level of injury.
• Determine is completely or incompletely injured.
• Determine ASIA Impairment Scale Grade.

Non-Traumatic Spinal Cord Disorders

• Includes syringomyelia, spina bifida, myelitis, spinal epidural abscess, spinal epi/subdural hematoma and SC infarction.

Syringomyelia

• It is characterized by a fluid-filled gliosis-lined cavity starting in the central canal.
• It has associated disruption of central structures and anterior horn of gray matter.
• Etiology is unclear and Irregular cavity is shown on diagnostic studies such as MRI and CT.
• Is associated with spinal column and/or brainstem abnormalities.
• Presents during the third and fourth decades of life but can occur in childhood
• Progression: Long motor tracts affected or Sensory tracts affected (UE >LE)
• Post-traumatic Syringomyelia: include symptoms from above or below the original injury.

Syringomyelia Treatment

• Conservative treatment includes avoiding high-force isometric contractions, valsalva expiration, head elevation at night, and maintaining a neutral neck position.
• Surgical interventions include decompression, shunt replacement, and tumor resection with radiation (intramedullary spinal cord tumors).

Spina Bifida

• Spina bifida aperta is visible or open. Spina bifida occulta is hidden or not visible
• Spina Bifida Aperta: Myelomeningocele more severe. characterized by Protruding spinal meninges and spinal cord through a defect in the vertebral column.

Clinical Findings of Spina Bifida

• The degree of motor and/or sensory loss varies
• Musculoskeletal deformities
• High risk: Neurogenic bowel and bladder, UTIs, latex allergies, and Arnold Chiari type II, hydrocephalus
• No two patients are clinically Identical
• Are at high risk for loss of function over time

Medical Treatment for Spina Bifida

• Treatment options include surgical closure of myelomeningocele, surgical correction of orthopedic deformities, placement of VP shunt, medications for bowel and bladder managment, and fetal meningomyelocele repair.

Prognosis of Spina Bifida

• Despite surgery, affected nerves may still not function normally.
• Individuals with spinal bifada have a typically normal intelligence.
• Due to risk of hydrocephalus and meningitis: Learning problems and Seizure disorders
• Spinal cord issues can develop later in life: Rapid growth during puberty, ↑ risk of progressive neurological impairments, Orthopedic problems (scoliosis, foot or ankle deformities, dislocated hips, and joint tightness or contractures.

Tethered Cord

• It occurs from scarring of the spinal cord and/or meninges to the overlying dura or skin and resulted Traction on neural structures.
• Often with the following Signs and symptoms: Deterioration of “normal” gait pattern , Loss of strength ,Pain along a dermatome or Change in bowel/bladder sphincter control
• May be a Deteriorate with “normal” gait pattern Initial onset or worsening of spasticity

This quiz covers the anatomy and function of the spinal cord, including its structures, meningeal layers, and nerve roots. Questions address the impact of injuries and lesions on spinal cord function. Test your knowledge of spinal cord components and their roles in sensory and motor pathways.