Meningeal Irritation and Signs

INTRODUCTION

Meningeal signs (meningismus) are physical findings indicating inflammation of the meninges (meningitis, subarachnoid hemorrhage). Their presentation varies significantly by age, being subtle in infants and classic in older children.

A. SIGNS IN INFANTS (< 12–18 MONTHS)

Classic signs like neck rigidity are notoriously absent or difficult to elicit in infants. The features are often nonspecific.

1. Clinical Features

• Paradoxical Irritability: The hallmark sign. The infant cries more when held or handled by the mother (due to movement of inflamed meninges) and settles when placed quietly on the bed. This is in contrast to systemic illness where holding soothes the child.
• Bulging Anterior Fontanelle: Tense, elevated, and non-pulsatile (loss of normal pulsations). Best assessed in the sitting position when the infant is not crying.
• Altered Tone:
  • Early: Hypotonia.
  • Late: Opisthotonus (arching of the back).
• High-Pitched "Neuro" Cry: A distinct, shrill cry.
• Staring Look: "Sun-setting" sign if intracranial pressure is significantly raised.

2. Elicitation

• Fontanelle Palpation: Palpate gently while the infant is upright and calm.
• Suspension Test (Lesage's Sign): When the infant is lifted by the axillae, the legs are drawn up (flexed) and the neck extends, instead of the normal bicycling or dangling movement.

B. SIGNS IN OLDER CHILDREN (> 2 YEARS)

In children with closed fontanelles, the classic triad of meningeal irritation can be elicited.

1. Nuchal Rigidity (Neck Stiffness)

The earliest and most consistent sign.

• Definition: Involuntary resistance to passive flexion of the neck.
• Elicitation:
  • Place the child supine without a pillow.
  • Stabilize the chest with one hand.
  • Place the other hand under the occiput and gently attempt to flex the neck to bring the chin to the chest.
• Positive Sign: Resistance is felt, pain is elicited, or the child is unable to touch the chin to the chest.

2. Kernig’s Sign

• Elicitation:
  • Patient supine.
  • Flex the hip and knee to 90°.
  • Slowly extend the knee while keeping the hip flexed.
• Positive Sign: Extension of the knee beyond 135° is limited by pain and spasm in the hamstring muscles.

3. Brudzinski’s Signs

a. Brudzinski’s Neck Sign (Symphysis Sign)

• Elicitation: Passive flexion of the neck (as when testing nuchal rigidity).
• Positive Sign: Involuntary flexion of the hips and knees.

b. Brudzinski’s Leg Sign (Contralateral Reflex)

• Elicitation: Passive flexion of one hip and knee.
• Positive Sign: Involuntary flexion of the contralateral leg.

4. Tripod Sign (Amoss Sign)

• Elicitation: Ask the child to sit up in bed.
• Positive Sign: The child cannot sit upright without support; they place both hands behind them (like a tripod) to support the trunk and prevent flexion of the spine/meninges.

C. PSEUDO-NECK RIGIDITY

1. Definition and Causes

Apparent neck stiffness not caused by meningeal inflammation.

• Causes:
  • Meningism: Neck stiffness accompanying systemic infection (e.g., Pneumonia, Pyelonephritis) without CSF inflammation.
  • Local Pathology: Retropharyngeal abscess, Cervical lymphadenitis, Torticollis.
  • Musculoskeletal: Cervical spondylitis, trauma.

2. How to Rule Out (Differentiation)

The key differentiator is the Plane of Movement.

3. Kiss the Knee Test

• In true meningitis, the child cannot touch their lips to their knee due to spinal stiffness. In pseudo-rigidity (if cervical only), thoracolumbar flexibility may be preserved.