What are the differential diagnoses for neck stiffness in an adult, especially when accompanied by fever, headache, photophobia, altered mental status, or neurological deficits?

Differential Diagnosis of Neck Stiffness

Bacterial meningitis is the most critical diagnosis to exclude immediately when evaluating neck stiffness, particularly when accompanied by fever, headache, altered mental status, or photophobia, as delayed treatment significantly increases mortality. 1

Life-Threatening Conditions (Immediate Exclusion Required)

Bacterial Meningitis

• The classic triad of fever, neck stiffness, and altered mental status is present in only 41-51% of adults with bacterial meningitis, meaning absence of all three features does NOT exclude the diagnosis 1
• Headache (58-87%), fever >38°C (77-97%), and altered mental status (30-69%) are the most common presenting features, but each can be absent 1
• Kernig and Brudzinski signs have very low sensitivity (9-11%) and should not be used to rule out meningitis 1
• Petechial or purpuric rash occurs in 20-52% of cases and indicates meningococcal infection in >90% when present 1
• Lumbar puncture with CSF examination is mandatory unless contraindications exist; do not delay antibiotics while awaiting imaging or LP 1

Meningococcal Septicemia

• Presents with fever, petechiae, purpura, and shock in approximately 20% of invasive meningococcal disease cases 1
• Associated with significantly worse outcomes than isolated meningitis 1
• Leg pain, cold extremities, and abnormal skin color are early warning signs in children that may precede classic meningeal signs 1

Epidural Abscess

• Progressive neurologic deficits with constitutional symptoms (fever, elevated ESR/CRP) 2
• Risk factors include IV drug use, immunosuppression, recent spinal procedures 2
• Requires emergency MRI and immediate neurosurgical consultation 2

Vertebral Osteomyelitis/Discitis

• Fever, elevated inflammatory markers (ESR/CRP), vertebral body tenderness on palpation 2
• History of bacteremia, IV drug use, or immunocompromised state 2

Subarachnoid Hemorrhage

• Thunderclap headache with neck stiffness requires immediate non-contrast head CT 3
• May present without visual disturbances, weakness, or speech deficits 3

Serious Neurological Conditions

Spinal Cord Compression from Malignancy

• Intractable neck pain with progressive neurologic deficits (weakness, sensory changes) 2, 4
• Constitutional symptoms (weight loss, night sweats), history of known malignancy 2
• Pediatric patients with acquired torticollis or focal neurologic signs require consideration of malignancy 4
• Lymphadenopathy (cervical or mediastinal) may accompany spinal involvement 4

Cervical Myelopathy

• Always test for hyperreflexia, Babinski sign, and gait disturbance to avoid missing myelopathy masquerading as radiculopathy 2
• Progressive weakness, sensory changes below the level of compression 2

Inflammatory/Infectious Conditions

Aseptic Meningitis

• Headache, photophobia, neck stiffness, nausea/vomiting, occasionally fever 1
• Mental status should be normal, distinguishing it from encephalitis 1

Encephalitis

• Altered mental status distinguishes this from aseptic meningitis 1
• May present with fever, headache, neck stiffness plus confusion or behavioral changes 1

Cervical Lymphadenitis/Deep Neck Infection

• Swollen lymph nodes with pain on swallowing suggests inflammatory or infectious process requiring investigation 5
• May be accompanied by elevated CRP 5

Mechanical/Musculoskeletal Causes

Cervical Disc Herniation with Radiculopathy

• Dermatomal pain, sensory loss, and motor weakness in specific nerve root distribution 2
• Degenerative changes are present in 85% of asymptomatic individuals over 30 years; imaging findings must correlate clinically 2, 3

Cervical Spondylosis/Foraminal Stenosis

• Progressive radicular symptoms from osteophytes or facet arthropathy 2
• Age-related degenerative process 2

Whiplash Injury (Cervical Sprain/Strain)

• History of rapid hyperextension-hyperflexion trauma, typically motor vehicle collision 6
• Neck pain with restricted mobility, headache common 6
• Neurological symptoms occur in 6.84% of cervical sprain patients; new deficits after initial presentation are rare 6
• Annual incidence up to 600 per 100,000 in Western populations 6

Cervicogenic Headache

• Pain originates in neck and spreads to ipsilateral oculo-fronto-temporal area 3
• Pain provoked by cervical movements (not posture), reduced cervical range of motion, myofascial tenderness 3
• Affects 4% of general population, up to 20% of chronic headache patients 3

Red Flags Requiring Urgent Imaging (MRI Cervical Spine)

The following features mandate immediate MRI evaluation: 5, 2

• Elevated inflammatory markers (CRP, ESR) with neck pain 5
• Constitutional symptoms (fever, weight loss, night sweats) 2
• History of malignancy or immunosuppression 2
• IV drug use 2
• Progressive or severe neurologic deficits 2
• Intractable pain unresponsive to conservative therapy 5, 2
• Vertebral body tenderness on palpation 2

Diagnostic Approach Algorithm

1. Immediate assessment for meningitis/sepsis:

   • Check vital signs, mental status, presence of rash 1
   • If fever + headache + altered mental status OR petechial rash present: obtain blood cultures, administer empiric antibiotics (ceftriaxone ± vancomycin) IMMEDIATELY, then perform LP 1, 7
   • Do not delay antibiotics for imaging unless signs of increased intracranial pressure 1, 7

2. Screen for red flags:

   • Fever, elevated CRP/ESR, constitutional symptoms, progressive neurologic deficits, history of malignancy/immunosuppression, IV drug use 5, 2
   • If ANY red flag present: obtain MRI cervical spine without contrast 5, 2

3. Neurological examination:

   • Test for hyperreflexia, Babinski sign, gait disturbance (myelopathy) 2
   • Assess for dermatomal sensory/motor deficits (radiculopathy) 2
   • Evaluate upper vs. lower extremity strength differential 4

4. If no red flags and normal neurological exam:

   • Consider mechanical causes (cervical strain, cervicogenic headache) 3, 8
   • Trial of conservative management with NSAIDs, physical therapy 3
   • Minimal response to NSAIDs indicates potential serious underlying condition 5
   • Reassess at 6-8 weeks; if persistent, consider MRI 2

Critical Pitfalls to Avoid

• Do not rely on absence of classic triad to exclude bacterial meningitis—only 41-51% have all three features 1
• Do not use Kernig/Brudzinski signs to rule out meningitis—sensitivity is only 9-11% 1
• Do not assume degenerative imaging findings are causative without clinical correlation—present in 85% of asymptomatic adults over 30 2, 3
• Do not miss myelopathy by failing to test for upper motor neuron signs 2
• Do not delay antibiotics in suspected meningitis while awaiting imaging or LP 1, 7
• Do not ignore elevated inflammatory markers—warrant further investigation even with mild symptoms 5