Clinical Synthesis

• Hornet/wasp stings puncture skin and can introduce Clostridium tetani spores, especially when wound care and tetanus prophylaxis are inadequate (as often happens with "local hospital" management that focuses on the sting/allergic reaction rather than tetanus status) - Mulholland and Greenfield's Surgery, ROSEN's Emergency Medicine.
• The incubation period for tetanus is typically 4-14 days (up to several months) - her spasms began at almost exactly the expected interval after the sting - Bailey and Love's Short Practice of Surgery; ROSEN's Emergency Medicine.
• Tetanus produces tetanospasmin-mediated loss of inhibitory control at the neuromuscular junction, causing violent, sustained contraction of agonist and antagonist muscle groups (opisthotonus, paravertebral muscle spasm). This is a well-documented cause of vertebral (usually thoracolumbar) compression fractures - the axial paraspinal muscles are powerful enough to crush vertebral bodies during tetanic spasm, a phenomenon reported since the 1950s and still seen in case series from India today - ROSEN's Emergency Medicine: "Spasms can cause vertebral and long-bone fractures and tendon rupture"; Grainger & Allison's Diagnostic Radiology: "Vertebral body compression fractures, particularly in the thoracolumbar region... very occasionally occur" with violent muscle contraction/severe tetanus. Multiple case reports (PMID 8071559, and a 2022 case series on PMC9587697) describe exactly this mechanism, most often in older, incompletely immunized adults - matching her age and profile.
• A rheumatology differential table explicitly lists tetanus as presenting with "recent wound; stiffness of neck; difficulty swallowing; spasm of facial muscles; headache" - so her current headache and backache are consistent with ongoing/resolving tetanus-related muscular and autonomic irritability rather than being an unrelated new problem - Firestein & Kelley's Textbook of Rheumatology.

Interpreting her current complaints (headache + backache, no fever/vomiting/dizziness, stable vitals, intact neuro exam)

1. Mechanical/musculoskeletal backache from the L1 compression fracture itself - fracture pain, paraspinal muscle spasm/guarding, and possibly early postural change; common in osteoporotic elderly women.
2. Tension-type headache secondary to pain, muscle spasm, and disturbed sleep - a common accompaniment of severe back pain and residual generalized muscle tension in the recovery phase of tetanus.
3. Residual mild autonomic/muscular irritability of tetanus - autonomic dysfunction (tachycardia, labile BP, diaphoresis, headache) can persist for days after the acute spasm phase even as spasms themselves subside - ROSEN's Emergency Medicine.
4. Medication effect - if she received tetanus immunoglobulin/toxoid, benzodiazepines, magnesium sulfate, or antibiotics (metronidazole) at the local hospital, headache is a recognized side effect of several of these.
5. Analgesic-related or dehydration-related headache, or uncontrolled blood pressure (worth confirming specifically, since "vitals stable" can still include a mildly elevated BP).
6. Less likely at day 10, but worth a quick check: residual effects of hornet-sting envenomation such as rhabdomyolysis/acute kidney injury, which have been reported after multiple hornet stings and can cause malaise, headache, and back discomfort - Brenner and Rector's The Kidney (renal failure reported after multiple hornet stings).

Suggested next steps

• Confirm tetanus immunization/treatment status - has she received tetanus toxoid and, if indicated, tetanus immunoglobulin, plus wound debridement and metronidazole/penicillin? If not fully treated, she remains at risk of relapse/worsening spasms and needs this addressed urgently.
• Re-examine the sting wounds for residual infection or retained material.
• Spine imaging review - confirm fracture stability, degree of vertebral height loss, and absence of cord/cauda equina involvement (MRI if any neurological change develops); assess for underlying osteoporosis, since a compression fracture from muscle spasm alone (rather than trauma) suggests weakened bone.
• Basic labs: renal function, CK (to rule out sting-related rhabdomyolysis), CBC, electrolytes (autonomic dysfunction/vomiting from earlier illness can cause derangement), blood pressure trend.
• Symptomatic management: analgesia (paracetamol first-line; avoid NSAIDs if renal function is uncertain), TLSO bracing or bed rest for fracture comfort, calcium/vitamin D and osteoporosis workup, physiotherapy once pain allows, and close neuro-monitoring for any new deficit.
• Watch for red flags that would change the picture: fever, vomiting, neck stiffness, altered sensorium, or new focal neurology - if any appear, urgent neuroimaging and CSF analysis are warranted to exclude CNS infection.

Key update: active tetanus is now unlikely

• Normal gag reflex on posterior pharyngeal stimulation is essentially the "spatula test" - touching the posterior pharyngeal wall and eliciting a normal gag (rather than a reflex spasm of the masseters) is a negative spatula test, which has ~94% sensitivity and 100% specificity for excluding tetanus.
• Soft masseter, no rigidity, full mouth opening = no trismus, no risus sardonicus, no nuchal/abdominal rigidity - these are the classic early and most consistent findings of generalized tetanus (present in 50-75% of cases as the presenting sign, and typically the persistent finding throughout the ~2-week illness course). Their complete absence, together with the negative gag/spatula response, makes ongoing tetanus very unlikely at this point.
• CDC/UpToDate/Mayo criteria all emphasize trismus + risus sardonicus + rigidity between spasms as the hallmark; "features that suggest another diagnosis" per UpToDate include muscle relaxation between episodes and absence of these tonic-contraction signs - which is exactly what she has.

Revised interpretation

Reassessing her current headache + backache

1. Backache - mechanical pain from the L1 compression fracture (most likely), reasonably managed with analgesia, bracing, and mobilization as tolerated.
2. Headache - in a 65-year-old woman with a new headache, I would specifically screen for giant cell (temporal) arteritis, since this age/sex group is the classic demographic and missing it risks permanent vision loss. Ask about scalp/temporal tenderness, jaw claudication, visual disturbance, and check ESR/CRP and temporal artery palpation. Beyond that, tension-type headache (from pain, poor sleep, muscle tension), analgesic-related headache, dehydration, or an uncontrolled blood pressure reading are more likely benign causes.

Suggested next steps

• ESR/CRP + temporal artery exam to screen for GCA given age and sex.
• Confirm blood pressure specifically (not just "stable") and basic metabolic panel/calcium (hypocalcemia or electrolyte disturbance can also cause muscle cramps and headache, and is worth excluding especially if renal function was affected by the earlier hornet stings).
• DEXA scan and osteoporosis workup (calcium, vitamin D, secondary causes) given a compression fracture in a postmenopausal woman.
• Continue analgesia and bracing for the L1 fracture; reassess neurology serially.
• If headache persists, worsens, or any new red flag (fever, neck stiffness, visual change, altered sensorium) appears, proceed to neuroimaging - but nothing currently mandates urgent CT/MRI brain.
• No indication currently for anti-tetanus escalation given the negative spatula test and soft masseter, but confirm her tetanus immunization/prophylaxis status was addressed at the local hospital for documentation purposes.