Differential Diagnosis in Neurology

9.4. Medical Causes of Lumbosacral Plexopathy

Vasculitis:

• General Features:
  • Usually a necrotizing vasculitis (PAN)
• Clinical Presentation:
  • Develops acutely
  • Painful; weakness and fixed sensory loss
  • Progresses in a stepwise manner
  • Constitutional symptoms associated; eosinophilia, weight loss, granuloma of the respiratory tract, retinitis, purpura, CNS involvement
• Differential Diagnosis:
  • Diabetic microvasculitis
  • SLE
  • Periarteritis nodosa
  • Sarcoid
  • Steroid responsive lumbosacral plexopathy
  • Wegener's granulomatosis
  • Pregnancy
  • Hereditary temperature sensitive plexopathy (AD)

Idiopathic Lumbosacral Plexitis

• General Features:
  • Age of onset is 30 months to 81 years of age
  • Monophasic and mild to a recurrent and severe course
  • Bimodal incidence:
    • Prior to age 20
    • Between 40–60
  • Mild trauma and viral illness have been reported to precede illness in some patients
  • Children in general have a monophasic course; adults usually have recurrences
  • Counterpart of neuralgia amyotrophic
• Clinical Presentation:
  • Abrupt onset of unilateral pain in the anterior thigh (lumbar plexitis), buttock and posterior thigh (sacral plexitis); some patients have more prolonged onset with recurrent bouts of pain
  • Muscle weakness within 5–10 days of onset of the pain; may progress for days to weeks; the pain resolves as weakness supervenes
  • Muscle weakness of L1–L4 roots most common, associated with positive femoral reverse SLR nerve test and absent quadriceps reflex
  • Lower plexus involvement; positive Tinel's sign at the sciatic notch and posterior popliteal fossa; weakness of the anterior tibialis, everters of the ankle and the extensor hallucis longus muscle. Absent ankle reflexes.
  • Paresthesias may occur after reduction of pain. Objective sensory loss may be subtle.
  • Process may be bilateral
  • Recovery is usually prolonged (over months) and is incomplete
  • Elevated sed rate
  • Occasional slight increase of protein in the cerebral spinal fluid

Diseases Associated with Lumbosacral Plexitis

• Following administration of serum
• May occur in patients with brachial amyotrophy
• Heroin IV (adulterated with quinine and Librium)
  • Symptoms often delayed after IV dose
  • Associated with rhabdomyolysis
  • Possible response to steroid

Proximal Diabetic Neuropathy

• General features:
  • Involvement of nerve roots and the lumbosacral plexus
  • 8% prevalence in Type I and II diabetic patients
  • Rarely the presenting feature of DM
  • Most common onset is sixth to seventh decade
  • Usually seen in Type I diabetes controlled by diet and oral hypoglycemic agents
  • Rare to have concomitant nephropathy, retinopathy or history of coma
• Clinical Presentation:
  • Severe anterior thigh pain is suffered early
  • Quadriceps weakness occurs over a few days to months
  • Sensory loss < weakness
  • Bilateral asymmetric involvement is frequent (usually after six weeks)
  • A history of 10–15 pound weight loss is seen
  • Knee jerks are absent; an occasional Babinski sign is noted
  • Persistent muscle deficit is noted although the majority of patients improve over a year
  • Recurrences occur
  • Sed rate is elevated in 20% of patients
  • CSF protein slightly elevated (120 mg% suggests nerve root involvement)
  • EMG:
    • Affected muscles demonstrate denervation
    • Demyelination and axonal loss in intramuscular nerves
  • Microangiopathic vasculitis has been recently demonstrated

Infections Affecting the Lumbosacral Plexus

• Abscess:
  • Bacterial abscess whose origin is the psoas or paraspinal muscles is rare
  • Perirectal abscess:
    • Immunocompromised patients
    • Prior rectal surgery
    • Fever in association with groin, abdominal or back pain
      • Usually sciatic nerve radiation
      • L4–S2 motor/sensory dysfunction
• Anogenital herpes simplex (higher roots; L1–L4)
• Herpes Zoster (L5; S1 roots)
• Tuberculosis (cold abscess; involving the psoas and iliacus muscle; T12–L4 roots)
• Pyelonephritis
• Appendicitis (upper roots of the plexus; characteristic iliopsoas spasm)
• Iliacus muscle abscess (following laparoscopy)
• Schistosomiasis japonicum (recurrent)
• Lyme's disease (L5 root most common)
• Brucellosis (recurrent L5 root)
• CMV (entire lumbosacral plexitis; HIV associated)
• Syphilis (dorsal root entry zone; meninges) stage II; HIV associated
• Epidural abscess (surgery; catheters; osteomyelitis)

Anogenital Herpes Simplex

• May involve lower motor neurons of the sacrococcygeal plexus
• Paresthesias and sensory loss of the perineum, buttocks posterior thighs
• Urinary retention, constipation and erectile dysfunction
• Reduced tone of the anal sphincter: sensory loss in sacral dermatomes; loss of the bulbocavernous reflex
• Dermatomal leg weakness and sensory loss
• More diffuse weakness is attributable to associated myelitis; possible demyelinating process
• The anogenital primary lesion may be on the cervix
• Herpes Simplex Type 2 > 1
• Mild meningeal irritation noted in some patients
• Lymphocytic pleocytosis
• Confirmed by PCR
• Symptoms last 10 days to 3 weeks; good recovery
• Approximately 1% of women with primary anogenital infection develop plexopathy
• Most frequent incidence is in males with herpetic proctitis
• Rare in recurrent herpetic attacks

CMV Infection

• Lumbosacral plexitis noted in severely ill HIV patients
• CD4 counts less than 200/mm³; frequently less than 50 mm³
• Severe pain and paresthesias in lumbar sacral areas; sexual dysfunction
• Associated retinitis

IV Drug abuse

• Pyogenic organisms: staph aureus most common
• Affects the disc space (end artery)
• Severely painful (vibration of the bed causes pain); very positive meningeal irritation signs
• Involvement of anterior and posterior vertebral space: positive enhancement with gadolinium on MRI of muscle and infected areas
• Lumbosacral roots themselves may enhance with MRI

EBV Infection

• Gluteal or thigh pain
• Leg weakness; decreased knee and ankle reflexes
• CSF: increased lymphocytes; slightly elevated protein

Lyme Disease

• Buttock pain
• Sciatic nerve weakness

Hereditary Liability to Pressure Palsy

• Chromosome 17 deletion (reciprocal of duplication of HSMN I)
• Less frequently seen than in upper extremity
• Clinical presentation:
  • Pain in the buttock and leg
  • Weakness of affected myotomes
  • Loss of reflexes
  • Sensory loss of affected dermatomes
• Women may become symptomatic puberally
• Rare to have severe pain
• Patients may not recall the episode of nerve compression
• Distal > proximal weakness