Unit 2 · Diagnosis & dose
Grade the muscle, then choose the dose
This unit introduces the five-part framework used throughout the rest of the module and applies its first two components. You will learn to assess a muscle before treating it, grade its activity on a standard scale, and use that grade — not habit — to inform the dose you select.
Framing
The 5 D's: a framework for every treatment decision
Every clinical decision in this module — from the first assessment to the final injection point — sits inside a five-part framework. This unit introduces all five; units 3 to 5 assume you know them.
- 1 — Diagnosis
- Muscle assessment and grading.
- 2 — Dose
- Unit selection and rationale.
- 3 — Depth
- Target muscle plane.
- 4 — Direction
- Entry point and needle angle.
- 5 — Distribution
- Spread, placement and extrusion.
Applied consistently, the 5 D's reduce variability, support clinical reasoning, and build a defensible treatment rationale — one you can articulate at review, not just execute at the chairside.
This unit covers Diagnosis and Dose. Depth, Direction and Distribution follow in Unit 3.
Learn · Diagnosis
Diagnosis is a structured assessment, not an assumption
Diagnosis means a clinical assessment of the muscle or muscle group being considered for treatment. This is not passive observation — it is a structured evaluation that should occur before every treatment session, not assumed from prior visits.
- Dynamic assessment
- Paramount. Ask the patient to produce the expression associated with the target concern — frowning, raising brows, smiling, clenching. Observe which muscles activate, their relative strength, and whether any compensatory patterns are present.
- Static assessment
- Follows dynamic assessment. Evaluating lines at rest reveals where dermal damage has already occurred from repeated muscle contraction. Static lines at rest do not resolve fully with neuromodulator treatment alone and require expectation-setting with the patient.
A patient who lifts their brows substantially to compensate for early brow ptosis has a very different clinical picture from one with a genuinely overactive frontalis, even though both may present with visible forehead lines on dynamic assessment. Distinguishing the two is the point of assessing before every session rather than relying on what was observed last visit.
One patient's glabellar area is line-free at rest but shows deep furrows on frowning. A second patient shows visible lines in the glabella even with the face fully relaxed. Which statement correctly applies the diagnosis framework to these two findings?
Select an option to commit. The reasoning appears afterwards.
Dynamic assessment is paramount and comes first — it is how you observe which muscles activate and at what strength. Static assessment follows, and it carries its own clinical weight: lines still visible at rest indicate dermal damage from repeated contraction that has already occurred, not simply muscle activity that can be relaxed away.
This is why the two patients are not interchangeable despite both presenting with glabellar lines. The second patient needs expectation-setting before treatment, because neuromodulator treatment relaxes the muscle — it does not repair dermal damage that static lines represent.
Predict · Muscle strength grading
Grading the muscle changes the dose you choose
Dose decisions should be informed by grade. A Grade 1 frontalis requires a materially different approach to a Grade 4. Before the grading scale is set out in full, commit to an answer using the case below.
A patient's forehead is unlined at rest. When they raise their brows, moderate lines become visible along the expression, but the lines disappear completely once the face relaxes. Using the 1–4 muscle strength grading scale, how would you grade this muscle — and why does the grade matter for the dose that follows?
Hold your answer before you open this. The value is in having committed to a grade first.
The scale runs Grade 1 — minimal activity, fine surface lines only; Grade 2 — moderate activity, visible lines on expression; Grade 3 — strong activity, visible lines at rest in some positions; and Grade 4 — dominant activity, deep static lines at rest. The muscle described here — lines that appear only on animation and resolve fully once the face relaxes — is Grade 2.
The grade matters because dose decisions should be informed by it, not assumed from a previous visit. A Grade 1 muscle and a Grade 4 muscle in the same treatment area call for materially different approaches, and documenting the grade at each session is what makes a dose adjustment at review evidence-based rather than habitual.
Document grading in the clinical record. This enables meaningful comparison at review and supports evidence-based dose adjustments over treatment cycles, rather than a dose decision made from memory of how the muscle presented last time.
When grading muscle activity prior to treatment, a Grade 3 muscle is best described as:
Select an option to commit. The reasoning appears afterwards.
Grade 3 sits between moderate expression-only activity and dominant activity with deep static lines. It describes strong activity, with lines visible at rest in some positions — the muscle has begun to leave a static signature, but not the fully established deep lines of Grade 4.
The grade is what a dose decision should be built on. A Grade 3 muscle sits closer to the upper end of a treatment area's indicative BTX-A reference unit range than a Grade 1 or Grade 2 presentation in the same area, and the grade recorded today is what the next review compares against.
Learn · Dose
Dose is a clinical decision, not a fixed prescription
Dosing is not a fixed prescription — it is a clinical decision informed by muscle grade, treatment area, patient anatomy, prior treatment history, and desired outcome.
Starting conservatively and adjusting at review is preferable to over-treating and managing an adverse outcome. A dose you can safely increase at the next visit is a better starting position than one you have to explain away.
Every figure in the table below is an indicative BTX-A reference unit range — a starting point for clinical reasoning, not a prescription. Current product-specific prescribing information governs the dose actually administered.
| Treatment area | Muscle(s) | Type | Indicative BTX-A reference units | Points | Notes |
|---|---|---|---|---|---|
| Horizontal forehead lines | Frontalis | Elevator | 10–20 units | 4–6 | Treat conservatively. Always assess brow position. Avoid inferior injection points below mid-pupil line. |
| Glabellar complex ("11s") | Corrugator & procerus | Depressor | 20–30 units total | 5 | Standard 5-point technique. Corrugators bilateral (2 pts each), procerus central (1 pt). Treat simultaneously. |
| Lateral canthal lines ("crow's feet") | Orbicularis oculi | Sphincter | 8–20 units per side | 3–4 per side | Stay ≥1cm lateral to orbital rim. Inject superficially, subcutaneous plane. Treat bilaterally. |
| Brow shaping — medial depression | Corrugator (medial) | Depressor | 4–8 units per side | 1–2 per side | Advanced technique for brow shaping. Requires precise anatomical knowledge of corrugator origin. |
| Downturned mouth corners | Depressor anguli oris | Depressor | 2–5 units per side | 1 per side | Palpate the DAO carefully lateral to commissure. Avoid orbicularis oris — asymmetric lip droop risk. |
| Chin dimpling / peau d'orange | Mentalis | Depressor | 4–10 units total | 2 | Paired muscle bellies, central chin. Risk of chin ptosis with over-treatment. Frequently combined with DAO. |
| Vertical neck bands | Platysma | Depressor | 20–60 units total | Variable per band | Nefertiti lift technique. Multiple points along each visible platysmal band. Advanced — reassess at 4 weeks. |
| Bunny lines | Nasalis | Depressor | 4–8 units total | 2 | Commonly a compensatory response to glabellar treatment. Assess whether treating the cause addresses the effect. |
Two rows in this table are flagged as advanced techniques in their own right. Medial brow shaping requires precise anatomical knowledge of the corrugator origin and is a distinct technique from standard glabellar treatment, not a variation of it. The platysma's Nefertiti lift technique uses multiple points along each visible band and, given the wider indicative BTX-A reference range involved, should be reassessed at four weeks rather than the standard review window.
A practitioner is planning treatment of the glabellar complex ("11s") for a patient with strong corrugator and procerus activity. Using the dose reference table of indicative BTX-A reference units, which statement correctly describes the standard approach?
Select an option to commit. The reasoning appears afterwards.
The standard glabellar complex technique is a 5-point approach: the corrugators bilaterally at two points each and the procerus centrally at one point, treated simultaneously, within an indicative BTX-A reference range of 20–30 units total.
Reading the dose table by treatment area rather than by number matters in practice. The 8–20 units per side and 4–8 units per side ranges belong to different treatment areas entirely — lateral canthal lines and medial brow shaping respectively — and transposing a figure from the wrong row is a dosing error, not a rounding difference.
Unit 2 summary
Clinical takeaways
- Diagnosis is structured and repeated. Dynamic assessment comes first and is paramount; static assessment follows, revealing dermal damage that treatment alone will not resolve. Assess before every session, not from memory of the last one.
- Grading drives the dose decision. The 1–4 muscle strength scale — from minimal activity to dominant activity with deep static lines — should be documented at every visit so dose adjustments at review are evidence-based, not habitual.
- Dose is a clinical judgement, not a fixed number. It is informed by grade, treatment area, patient anatomy, prior history and desired outcome. Starting conservatively and adjusting at review is preferable to managing an over-treatment outcome.
- Every figure in the dose table is an indicative BTX-A reference unit range. It is a starting point for clinical reasoning by treatment area, read by row — never a prescription, and never transposed between rows or between formulations.