Questions & Answers

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Media Gallery

Muscle groups, surface anatomy, peripheral sensory innervation, and dermatomes of the anterior lower limb. This image should be correlated with Tables 1 and 2 in the text. Image courtesy of Nicholas Y. Lorenzo, MD.
Muscle groups, surface anatomy, peripheral sensory innervation, and dermatomes of the posterior lower limb. This image should be correlated with Tables 1 and 2 in the text. Image courtesy of Nicholas Y. Lorenzo, MD.
Conus/epiconus infarction in the setting of sickle cell crisis. Image courtesy of Matthew J. Baker, MD.
Conus/epiconus infarction in the setting of sickle cell crisis in the same patient shown in the above image. Image courtesy of Matthew J. Baker, MD.
Conus/epiconus infarction in the setting of sickle cell crisis in the same patient shown in the images above. Image courtesy of Matthew J. Baker, MD.
Illustration demonstrating the relevant anatomy of the cauda equina region
Illustration demonstrating an example of cauda equina syndrome secondary to a spinal neoplasm
Sagittal MRI of a patient with cauda equina syndrome secondary to a large lumbar disk herniation
Epidural abscess with effacement of thecal sac in a 56-year-old man.

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Table 1. Symptoms and Signs of Conus Medullaris and Cauda Equina Syndromes

	Conus Medullaris Syndrome	Cauda Equina Syndrome
Presentation	Sudden and bilateral	Gradual and unilateral
Reflexes	Knee jerks preserved but ankle jerks affected	Both ankle and knee jerks affected
Radicular pain	Less severe	More severe
Low back pain	More	Less
Sensory symptoms and signs	Numbness tends to be more localized to perianal area; symmetrical and bilateral; sensory dissociation occurs	Numbness tends to be more localized to saddle area; asymmetrical, may be unilateral; no sensory dissociation; loss of sensation in specific dermatomes in lower extremities with numbness and paresthesia; possible numbness in pubic area, including glans penis or clitoris
Motor strength	Typically symmetric, hyperreflexic distal paresis of lower limbs that is less marked; fasciculations may be present	Asymmetric areflexic paraplegia that is more marked; fasciculations rare; atrophy more common
Impotence	Frequent	Less frequent; erectile dysfunction that includes inability to have erection, inability to maintain erection, lack of sensation in pubic area (including glans penis or clitoris), and inability to ejaculate
Sphincter dysfunction	Urinary retention and atonic anal sphincter cause overflow urinary incontinence and fecal incontinence; tend to present early in course of disease	Urinary retention; tends to present late in course of disease

Table 2. Pain and Deficits Associated with Specific Nerve Roots

Nerve Root	Pain	Sensory Deficit	Motor Deficit	Reflex Deficit
L2	Anterior medial thigh	Upper thigh	Slight quadriceps weakness; hip flexion; thigh adduction	Slightly diminished suprapatellar
L3	Anterior lateral thigh	Lower thigh	Quadriceps weakness; knee extension; thigh adduction	Patellar or suprapatellar
L4	Posterolateral thigh, anterior tibia	Medial leg	Knee and foot extension	Patellar
L5	Dorsum of foot	Dorsum of foot	Dorsiflexion of foot and toes	Hamstrings
S1-2	Lateral foot	Lateral foot	Plantar flexion of foot and toes	Achilles
S3-5	Perineum	Saddle	Sphincters	Bulbocavernosus; anal

Table 3. Root and Peripheral Nerve Innervation of the Lumbosacral Plexus

Muscle	Nerve	Root
Iliopsoas	Femoral	L2, 3, 4
Adductor longus	Obturator	L2, 3, 4
Gracilis	Obturator	L2, 3, 4
Quadriceps femoris	Femoral	L2, 3, 4
Anterior tibial	Deep peroneal	L4, 5
Extensor hallucis longus	Deep peroneal	L4, 5
Extensor digitorum longus	Deep peroneal	L4,5
Extensor digitorum brevis	Deep peroneal	L4, 5, S1
Peroneus longus	Superficial peroneal	L5, S1
Internal hamstrings	Sciatic	L4, 5, S1
External hamstrings	Sciatic	L5, S1
Gluteus medius	Superior gluteal	L4, 5, S1
Gluteus maximus	Inferior gluteal	L5, S1, 2
Posterior tibial	Tibial	L5, S1
Flexor digitorum longus	Tibial	L5, S1
Abductor hallucis brevis	Tibial (medial plantar)	L5, S1, 2
Abductor digiti quinti pedis	Tibial (lateral plantar)	S1, 2
Gastrocnemius lateral	Tibial	L5, S1, 2
Gastrocnemius medial	Tibial	S1, 2
Soleus	Tibial	S1, 2

Table 4. Cauda Equina Versus Conus Medullaris Syndrome

Features	Cauda Equina Syndrome	Conus Medullaris
Vertebral level	L2-sacrum	L1-L2
Spinal level	Injury to the lumbosacral nerve roots	Injury of the sacral cord segment (conus and epiconus) and roots
Severity of symptoms and signs	Usually severe	Usually not severe
Symmetry of symptoms and signs	Usually asymmetric	Usually symmetric
Pain	Prominent, asymmetric, and radicular	Usually bilateral and in the perineal area
Motor	Weakness to flaccid paralysis	Normal motor function to mild or moderate weakness
Sensory	Saddle anesthesia, may be asymmetric	Symmetric saddle distribution, sensory loss of pin prick, and temperature sensations (Tactile sensation is spared.)
Reflexes	Areflexic lower extremities; bulbocavernosus reflex is absent in low CE (sacral) lesions	Areflexic lower extremities (If the epiconus is involved, patellar reflex may be absent, whereas bulbocavernosus reflex may be spared.)
Sphincter and sexual function	Usually late and of lesser magnitude; lower sacral roots involvement can cause bladder, bowel, and sexual dysfunction	Early and severe bowel, bladder, and sexual dysfunction that results in a reflexic bowel and bladder with impaired erection in males
EMG	Multiple root level involvement; sphincters may also be involved	Mostly normal lower extremity with external anal sphincter involvement
Outcome	May be favorable compared with conus medullaris syndrome	The outcome may be less favorable than in patients with CES

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Author

Segun Toyin Dawodu, JD, MD, MS, MBA, LLM, FAAPMR, FAANEM Attending Interventional Physiatrist, Wellspan Health

Segun Toyin Dawodu, JD, MD, MS, MBA, LLM, FAAPMR, FAANEM is a member of the following medical societies: American College of Sports Medicine, American Academy of Physical Medicine and Rehabilitation, Royal College of Surgeons of England, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, American Medical Informatics Association, Association of Academic Physiatrists, International Society of Physical and Rehabilitation Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Kirsten A Bechtel, MD Associate Professor of Pediatrics, Section of Pediatric Emergency Medicine, Yale University School of Medicine; Co-Director, Injury Free Coalition for Kids, Yale-New Haven Children's Hospital

Kirsten A Bechtel, MD is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Nothing to disclose.

Michael S Beeson, MD, MBA, FACEP Professor of Emergency Medicine, Northeastern Ohio Universities College of Medicine and Pharmacy; Attending Faculty, Akron General Medical Center

Michael S Beeson, MD, MBA, FACEP is a member of the following medical societies: American College of Emergency Physicians, National Association of EMS Physicians, Council of Emergency Medicine Residency Directors, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Scott D Hodges, DO Consulting Surgeon, Department of Orthopedic Surgery, Center for Sports Medicine and Orthopedics

Scott D Hodges, DO is a member of the following medical societies: American Academy of Disability Evaluating Physicians, American Medical Association, American Osteopathic Association, American Spinal Injury Association, North American Spine Society, Southern Medical Association, Southern Orthopaedic Association, Tennessee Medical Association

Disclosure: Received royalty from Medtronic for consulting; Received royalty from Biomet Spine for consulting.

S Craig Humphreys, MD Orthopedic Spine Surgeon, Department of Orthopedic Surgery, Center for Sports Medicine and Orthopedics

S Craig Humphreys, MD is a member of the following medical societies: American Spinal Injury Association, Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American Medical Association, North American Spine Society, Southern Medical Association, Southern Orthopaedic Association, Tennessee Medical Association

Disclosure: Nothing to disclose.

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) Professor, Department of Orthopedic Surgery, University of Texas Medical School at Houston

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) is a member of the following medical societies: American Academy of Orthopaedic Surgeons, Orthopaedic Trauma Association, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

J Stephen Huff, MD, FACEP Professor of Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia School of Medicine

J Stephen Huff, MD, FACEP is a member of the following medical societies: American Academy of Neurology, American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Nicholas Lorenzo, MD, MHA, CPE Co-Founder and Former Chief Publishing Officer, eMedicine and eMedicine Health, Founding Editor-in-Chief, eMedicine Neurology; Founder and Former Chairman and CEO, Pearlsreview; Founder and CEO/CMO, PHLT Consultants; Chief Medical Officer, MeMD Inc; Chief Strategy Officer, Discourse LLC

Nicholas Lorenzo, MD, MHA, CPE is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Association for Physician Leadership

Disclosure: Nothing to disclose.

Additional Contributors

Milind J Kothari, DO Professor, Department of Neurology, Pennsylvania State University College of Medicine; Consulting Staff, Department of Neurology, Penn State Milton S Hershey Medical Center

Milind J Kothari, DO is a member of the following medical societies: American Academy of Neurology, American Neurological Association, American Association of Neuromuscular and Electrodiagnostic Medicine

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author Jason C Eck, DO, MS,to the development and writing of a source article.

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