Vocal Instability

Vocal instability is sometimes “discovered” in a person whose speaking voice sounds normal — or perhaps just slightly gravelly — during Vocal Capability Battery (VCB) elicitations (Part II of the Integrative Diagnostic Model). When instability appears in this context, it suggests that something neurological or neuromuscular may be contributing to the dysphonia.

This finding can redirect the clinician back to the History (Part I) or prompt a more detailed, insightful laryngeal examination (Part III). Importantly, it protects the examiner from making premature assumptions such as attributing symptoms to “reflux.” Instead, the clinician is guided to consider alternative explanations, including:

• Neuromuscular disease
• Early dystonia without phonatory arrest
• Subtle paresis
• Neuropathy, such as that seen in association with sensory neuropathic cough

How to Elicit Vocal Instability

The examiner models sustained phonation at various pitches, listening for features such as:

• A “glitch” or catch
• Wavering or tremor
• In-and-out vocal fry
• Other irregularities in steadiness

When You Describe an “Unstable” Voice, What does that Mean? 

With an unstable voice or loss of vocal control, the patient cannot, or cannot seem to reliably “find,” repeat more than once, or sustain the vocal task requested by the clinician—or even the voice production they themselves intend. Instability may present as wavering or wobbling, tremor, cutting in and out, pitch that drifts uncontrollably when trying to hold a note, or a jittery, quivery quality.

When vocal instability is observed, there are three main possible explanations:

1. Least likely: Poor Rapport of the Person with His or Her Voice

This is better thought of as poor control and inconsistency rather than instability. It is a deficit of knowing “how to work the pipes.”

• • The individual simply does not know how to coordinate the voice effectively. During the VCB—Part II of the Integrative Diagnostic Model —such a patient shows sincere effort but struggles with poor pitch matching or lacks awareness of what is being asked and how to produce it.  They may even ask, after attempting to reproduce the clinician’s elicitation: “Is that what you wanted?” 
  • With teaching and training—even brief coaching during the evaluation—called trial therapy—performance may improve. 

2. Occasional but Crucial to Identify: Functional / Non-Organic Explanation

• • In some cases, the problem is created or sustained by the patient (consciously or unconsciously) because it provides a secondary gain: loss of voice helps them avoid work, qualify for disability, or win a lawsuit.

• • In the VCB, this often shows up as latency (odd delays before responding despite multiple prompts) or nearly identical responses to very different vocal tasks that the clinician models for the patient to reproduce.

• • For example: when the clinician calls out a loud “HEY!” and asks the patient to repeat back, he or she may, after hesitation, respond with an even softer voice than the one they arrived with. At times, production is so unusual or “vocally illogical” that even untrained observers would find it unconvincing. 

3. Most Important: Neurological, Muscular, or Neuromuscular Disorder

• • Here, the patient shows sincere effort with no latency, but remains unable to succeed. Each attempt is consistent with the others—yet consistently abnormal.

• • Typical features include quivery “gravel,” tremor, or “glitches” in voice production—all of which are convincing to the voice-aware examiner.

• • Underlying causes may be relatively benign with respect to overall health, such as widened vibrato in the aging singer, essential tremor, or laryngeal dystonia (spasmodic dysphonia). However, instability may also signal more serious disease, such as ALS, Parkinson’s disease, or a tumor pressing on a nerve.