loss of recent memory after a fall on head, fall within 2 hours

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Based on authoritative textbook sources, here is a focused clinical overview:

Loss of Recent Memory After a Head Fall — Concussion / Mild TBI

What is Happening

Loss of recent (anterograde) memory within 2 hours of a head injury is a classic sign of concussion (mild TBI). Anterograde amnesia — inability to form new memories after the impact — is one of the hallmark features and may accompany or occur even without full loss of consciousness.

"Anterograde amnesia is a common sign of concussion and may result [from the injury]." — Plum and Posner's Diagnosis and Treatment of Stupor and Coma

Diagnostic Classification

Feature	Mild TBI / Concussion
Loss of consciousness	< 30 minutes (or none)
Anterograde amnesia	< 30 minutes surrounding the injury
Retrograde amnesia	May also be present
Alertness on exam	Usually returns to normal within minutes

Typical Presentation

The patient typically:

Becomes fully alert and attentive within minutes
Complains of headache, dizziness, nausea, faintness
Has a brief amnesic period (recent memory gap)
May have one episode of vomiting, blurred vision, or difficulty concentrating

This is described as having a "good prognosis with little risk of subsequent deterioration." — Harrison's Principles of Internal Medicine, 22E

When to Get a CT Scan (Red Flags)

CT imaging is justified if any of the following are present:

Persistent anterograde amnesia > 30 minutes
Age > 65 years
Two or more episodes of vomiting
Seizure
Concurrent drug or alcohol intoxication
Persistent confusion or focal neurologic signs
Underlying coagulopathy
Palpable skull fracture
Severe mechanism of injury

"Older age (>65 years), two or more episodes of vomiting, >30 min of retrograde or persistent anterograde amnesia, seizure, and concurrent drug or alcohol intoxication are sensitive (but not specific) indicators of intracranial hemorrhage that justify CT scanning." — Harrison's Principles of Internal Medicine, 22E

Key Clinical Concern: Rule Out Intracranial Hemorrhage

Loss of recent memory after a fall, especially within 2 hours, raises concern for:

Epidural hematoma — classic "lucid interval" followed by deterioration
Subdural hematoma — may present with gradual cognitive decline
Cerebral contusion — focal injury with amnesia

Even if the patient appears well initially, the 2-hour window is critical — neurological deterioration can be rapid with an expanding hematoma.

Management

CT head without contrast — if any red flag is present (especially if amnesia > 30 min or persistent)
Neurological observation — monitor GCS, pupillary response, motor function
If CT negative and patient alert: can be discharged with a responsible adult, with written instructions to return if symptoms worsen
Consider MRI if CT negative but symptoms persist — MRI detects small hemorrhages and contusions missed on CT in ~27% of CT-negative cases
Biomarkers (GFAP, UCHL1) — emerging point-of-care tools for detecting intracranial injury

Bottom Line

Loss of recent memory within 2 hours of a head fall = concussion until proven otherwise, but intracranial hemorrhage must be actively excluded. Obtain CT head promptly if any red flag is present. The amnesia itself (anterograde type) is a sensitive — though not specific — indicator of significant intracranial pathology.

— Harrison's Principles of Internal Medicine, 22E | Plum and Posner's Diagnosis and Treatment of Stupor and Coma | Bradley and Daroff's Neurology in Clinical Practice

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