HINTS stroke in acute vestibular syndrome

HINTS

Apply the Kattah 2009 three-step HINTS exam (Head-Impulse, Nystagmus, Test-of-Skew) from three caller-assigned flags and return whether any dangerous central sign is present.

LIVE $0.005 USDC GET /api/calc/hints

Markdown: /docs/hints.md · Canonical: https://magentlab.com/docs/hints

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Apply the Kattah 2009 three-step HINTS exam (Head-Impulse, Nystagmus, Test-of-Skew) from three caller-assigned flags and return whether any dangerous central sign is present.

When to use

When an agent already has the three HINTS flags for a patient already in acute vestibular syndrome (AVS) as in Kattah 2009 and needs whether the published three-step exam is dangerous or benign. magent does not examine the patient.

When not to use

Not a medical device.
Not a stroke diagnosis. magent does not examine the patient.
For patients already in acute vestibular syndrome (AVS) as in Kattah 2009. The caller assigns the three HINTS flags.
This is three-step HINTS only. Not HINTS-plus (hearing). magent does not take hearing loss, eye/verbal/motor GCS, or mortality tables.
Not a substitute for neuroimaging.

Formula

dangerous iff head_impulse_normal or direction_changing_nystagmus or skew_deviation; benign iff not dangerous (Kattah 2009 three-step HINTS for acute vestibular syndrome; INFARCT: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test)

Citation

Title: HINTS to Diagnose Stroke in the Acute Vestibular Syndrome
Authors: Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE
Source: Stroke. 2009;40(11):3504-3510
DOI: 10.1161/STROKEAHA.109.551234

Worked example

All three flags false (benign peripheral pattern)

Given: direction_changing_nystagmus=falsehead_impulse_normal=falseskew_deviation=false

head_impulse_normal false (abnormal HIT implied)
direction_changing_nystagmus false
skew_deviation false
dangerous_any is false; dangerous is false; benign is true

Normal head-impulse only (dangerous central sign)

Given: direction_changing_nystagmus=falsehead_impulse_normal=trueskew_deviation=false

head_impulse_normal true is a dangerous central sign (INFARCT: Impulse Normal)
The other two flags are false
dangerous_any is true; dangerous is true; benign is false

Also searched as

HINTS exam
HINTS stroke
Head Impulse Nystagmus Test of Skew
Kattah 2009 HINTS
acute vestibular syndrome HINTS
INFARCT HINTS
HINTS AVS
central vs peripheral vertigo

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/hints?head_impulse_normal=false&direction_changing_nystagmus=false&skew_deviation=false

Full URL: https://api.magentlab.com/api/calc/hints?head_impulse_normal=false&direction_changing_nystagmus=false&skew_deviation=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/hints?head_impulse_normal=false&direction_changing_nystagmus=false&skew_deviation=false"

Parameters

Name	Type	Required	Description
`head_impulse_normal`	boolean	required	Normal horizontal head-impulse test (h-HIT) as assigned by the caller (Kattah 2009). true is a dangerous central sign (INFARCT: Impulse Normal). magent does not examine the patient.
`direction_changing_nystagmus`	boolean	required	Direction-changing nystagmus in eccentric gaze as assigned by the caller (Kattah 2009). true is a dangerous central sign (INFARCT: Fast-phase Alternating). magent does not examine the patient.
`skew_deviation`	boolean	required	Skew deviation / vertical ocular misalignment on cover test as assigned by the caller (Kattah 2009). true is a dangerous central sign (INFARCT: Refixation on Cover Test). magent does not examine the patient.

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/hints Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

1 to 25 items. Each item uses the same keys as the GET query parameters.
POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "direction_changing_nystagmus": "false",
      "head_impulse_normal": "false",
      "skew_deviation": "false"
    },
    {
      "direction_changing_nystagmus": "false",
      "head_impulse_normal": "false",
      "skew_deviation": "false"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/hints",
  "items": [
    {
      "benign": true,
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE",
        "doi": "10.1161/STROKEAHA.109.551234",
        "id": "kattah-2009",
        "pmid": "19762709",
        "source": "Stroke. 2009;40(11):3504-3510",
        "title": "HINTS to Diagnose Stroke in the Acute Vestibular Syndrome"
      },
      "formula": "hints",
      "formula_expression": "dangerous iff head_impulse_normal or direction_changing_nystagmus or skew_deviation; benign iff not dangerous (Kattah 2009 three-step HINTS for acute vestibular syndrome; INFARCT: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test)",
      "criteria": [
        {
          "factor": "head_impulse_normal",
          "met": false
        },
        {
          "factor": "direction_changing_nystagmus",
          "met": false
        },
        {
          "factor": "skew_deviation",
          "met": false
        },
        {
          "factor": "dangerous_any",
          "met": false
        }
      ],
      "dangerous": false
    },
    {
      "benign": true,
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE",
        "doi": "10.1161/STROKEAHA.109.551234",
        "id": "kattah-2009",
        "pmid": "19762709",
        "source": "Stroke. 2009;40(11):3504-3510",
        "title": "HINTS to Diagnose Stroke in the Acute Vestibular Syndrome"
      },
      "formula": "hints",
      "formula_expression": "dangerous iff head_impulse_normal or direction_changing_nystagmus or skew_deviation; benign iff not dangerous (Kattah 2009 three-step HINTS for acute vestibular syndrome; INFARCT: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test)",
      "criteria": [
        {
          "factor": "head_impulse_normal",
          "met": false
        },
        {
          "factor": "direction_changing_nystagmus",
          "met": false
        },
        {
          "factor": "skew_deviation",
          "met": false
        },
        {
          "factor": "dangerous_any",
          "met": false
        }
      ],
      "dangerous": false
    }
  ]
}

Response

Field	Type	Description
`formula`	string	hints
`formula_expression`	string	Kattah 2009 three-step HINTS: dangerous if any of the three caller-assigned central signs
`dangerous`	boolean	true iff any of head_impulse_normal, direction_changing_nystagmus, or skew_deviation is true (INFARCT). Not a stroke diagnosis.
`benign`	boolean	true iff none of the three central signs is true (not dangerous)
`criteria`	array	Per-flag rows plus dangerous_any (met iff any of the three flags is true)
`citation`	object	Kattah 2009 Stroke citation
`disclaimer`	string	Not-a-device notice

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "benign": true,
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE",
    "doi": "10.1161/STROKEAHA.109.551234",
    "id": "kattah-2009",
    "pmid": "19762709",
    "source": "Stroke. 2009;40(11):3504-3510",
    "title": "HINTS to Diagnose Stroke in the Acute Vestibular Syndrome"
  },
  "formula": "hints",
  "formula_expression": "dangerous iff head_impulse_normal or direction_changing_nystagmus or skew_deviation; benign iff not dangerous (Kattah 2009 three-step HINTS for acute vestibular syndrome; INFARCT: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test)",
  "criteria": [
    {
      "factor": "head_impulse_normal",
      "met": false
    },
    {
      "factor": "direction_changing_nystagmus",
      "met": false
    },
    {
      "factor": "skew_deviation",
      "met": false
    },
    {
      "factor": "dangerous_any",
      "met": false
    }
  ],
  "dangerous": false
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

HTTP	Code	When
400	`invalid_flag`	boolean clinical flags must be true or false Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

Related tools

Glasgow Coma Scale — Compute the Glasgow Coma Scale as the sum of caller-assigned eye, verbal, and motor integers. The 1974 or 1976 edition is required.
GCS-Pupils — Return the Brennan 2018 GCS-Pupils index as caller-assigned total GCS 3-15 minus pupil reactivity score (unreactive pupils 0, 1, or 2).
ROSIER — Sum the seven Nor 2005 ROSIER items from caller-assigned flags and return whether the score is greater than 0 (stroke more likely).

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
Execution is timeout-bounded and concurrency-capped.
Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.