What is the differential diagnosis for neck rigidity?

Differential Diagnosis of Neck Rigidity

Neck rigidity in adults must be considered a sign of bacterial meningitis until proven otherwise, particularly when accompanied by fever, altered mental status, or headache, though the absence of these features does not exclude serious pathology. 1

Life-Threatening Causes (Immediate Evaluation Required)

Bacterial Meningitis

• The classic triad of fever, neck stiffness, and altered consciousness is present in less than 50% of bacterial meningitis cases 1
• Individual symptoms (fever, headache, neck stiffness) are poor discriminators when considered independently 1
• Meningitis can present atypically with sudden behavioral disturbance, mimicking substance abuse, without fever or neck rigidity 1
• Elderly patients are more likely to have altered consciousness and less likely to have neck stiffness or fever 1
• Kernig's and Brudzinski's signs have high specificity (up to 95%) but very low sensitivity (as low as 5%) and should not be relied upon for diagnosis 1
• Leucocytosis may be an important diagnostic clue 1
• Urgent lumbar puncture and broad-spectrum antibiotics are required; antibiotic therapy should never be withheld while awaiting imaging or other investigations 1

Subarachnoid Hemorrhage (SAH)

• Neck stiffness evaluated ≤6 hours after symptom onset has a positive predictive value of 90% but a negative predictive value of only 69%, meaning its absence does not rule out SAH 2
• Between 6-72 hours after onset, the negative predictive value improves to 91% 2
• Neck stiffness may be the only diagnostic clue in patients with normal consciousness and no focal deficits 2
• The clinical impression that neck stiffness takes several hours to develop is supported by time-dependent test characteristics 2

Meningococcal Sepsis

• Can present with or without meningitis in 10-20% of patients 1
• Typical features include hypotension, altered mental state, and purpuric/petechial rash, though rash may be maculopapular 1
• 37% of meningococcal meningitis patients do not have a rash 1
• Patients can deteriorate rapidly with shock 1

Serious Non-Life-Threatening Causes

Cervical Spine Pathology with Instability

• Capsular ligament laxity causes excessive movement between cervical vertebrae, leading to chronic neck pain and stiffness 3
• Upper cervical spine (C0-C2) instability can cause nerve irritation, vertebrobasilar insufficiency with vertigo, tinnitus, dizziness, facial pain, and migraine 3
• Lower cervical spine (C3-C7) instability causes muscle spasms, crepitation, and paresthesia 3
• Elevated inflammatory markers (CRP) combined with neck pain warrant MRI evaluation to exclude inflammatory or infectious processes 4

Vertebral Osteomyelitis/Discitis

• Consider in patients with elevated inflammatory markers, history of IV drug use, or immunosuppression 5
• Requires MRI cervical spine without contrast for diagnosis 4, 5
• Vertebral body tenderness on palpation is a red flag 5

Cervical Spine Malignancy

• Metastatic disease or primary spinal tumors can present with neck rigidity 5
• Red flags include history of malignancy, constitutional symptoms, and intractable pain 5

Common Benign Causes

Whiplash-Associated Disorder (WAD)

• Results from rapid acceleration-deceleration mechanism of neck injury 1
• Symptoms include neck pain, point tenderness, stiffness, reduced range of motion 1
• Imaging has limited value in WAD when diagnosis relies primarily on clinical factors 1, 6
• Most cases improve within 7-8 weeks, though 50% may have persistent symptoms at one year 6
• MRI findings often overestimate injury severity and should not drive management without neurological symptoms 6

Cervical Radiculopathy

• Affects approximately 83 per 100,000 persons annually 5
• Causes combined neck, shoulder, and forearm pain in upper limb distribution 5
• 75-90% of cases resolve with conservative therapy (NSAIDs, physical therapy, activity modification) 5
• MRI cervical spine without contrast is indicated if symptoms persist beyond 6-8 weeks 5

Acute Stiff Neck in Children (Torticollis)

• In pediatric populations, caused by strangulation of vascularized tissue in uncovertebral zones at C2-C3 or C3-C4 7
• MRI shows high-intensity zones near external edges of discs that disappear within days 7
• Note: This guideline focuses on adults, but awareness of pediatric differences is important 1

Cervical Spondylosis/Degenerative Disc Disease

• Extremely common, affecting 53.9% of individuals aged 18-97 5
• Prevalence increases with age 5
• Degenerative changes are common in asymptomatic individuals and correlate poorly with symptoms 4

Facet Joint Arthropathy

• Causes localized mechanical pain, often unilateral, radiating to trapezius and upper back 5

Neurological Causes

Higher Brain Dysfunction/Frontal Lobe Disorders

• Neck rigidity can be a physical manifestation of higher brain hypo-function or frontal lobe dysfunction 8
• Association confirmed in patients with brain lesions, particularly those with Parkinsonism 8
• Provides important clues to brain function even as a minor clinical manifestation 8

Critical Clinical Approach

Red Flags Requiring Immediate Imaging (MRI Cervical Spine Without Contrast)

• Constitutional symptoms (fever, weight loss, night sweats) 5
• Elevated inflammatory markers 4, 5
• History of malignancy or immunosuppression 5
• History of IV drug use 5
• Progressive neurological deficits 5
• Intractable pain 5
• Vertebral body tenderness on palpation 5

When to Suspect Meningitis Despite Atypical Presentation

• Sudden onset of behavioral disturbance with clouding of consciousness, even without fever or typical neck rigidity 1
• Presence of leucocytosis 1
• Concern from referring physician or family member should always be taken seriously 1
• History of contact with another person with meningitis 1

Common Pitfalls to Avoid

• Do not delay antibiotics while awaiting CT or lumbar puncture results in suspected meningitis 1
• Do not rely on Kernig's or Brudzinski's signs to exclude meningitis 1
• Do not assume absence of fever or neck stiffness rules out bacterial meningitis 1
• Do not attribute atypical behavioral presentations solely to substance abuse without excluding meningitis 1
• Do not over-interpret degenerative changes on imaging in the absence of red flags 4