ENG & VNGPositional & Caloric

Tests

Measuring Nystagmus

• Speed (slope) of the slow phase in degrees per second (°/s)

Positions & Responses

• Sitting erect– Head in primary position

– With head turned R/L

• Supine

• Right lateral

• Left lateral

• Head hanging

•

• Eyes closed/eyes open

• NORMAL , symmetrical responses to head position = No resp. w/ eyes open– Eyes Closed and mentally busy:

– direction-fixed positional nys

– direction changing (w/ changein position)

– some intermittent, some persistent

Pathologic responses:

• direction changing in single position

• persistent in 3 or more of the 5 positions

• intermittent in 4 or more positions

• Speed of slow phase is 6 deg/s or more at greatest

Left Lateral Position: Eyes Closed

Erect Position: Eyes Closed

Right Lateral Position: Eyes Closed

Direction-Changing Across Positions

Right Lateral Position: Eyes Closed

Left Lateral Position: Eyes Closed

Direction Changing Nystagmus within one position

Head Hanging Position: Eyes Closed

Abnormalities:

• Positional nys w/ eyes open: CNS lesions• Direction-fixed positional nys.: peripheral

– differs from spont. in that it varies in intensity with position, or is absent in some positions.

– appears in vestibular disease, e.g. Meniere's

– does not show which side is abnormal.

• Direction-changing nystagmus in a single position.– CNS

– Positional alcohol nystagmus

Positional Alcohol

Nystagmus• Top 2

tracings: 1 hour post ingestion

• Lower 2 tracings: 6 hours post ingestion

Right Lateral Position: Eyes Closed

Right Lateral Position: Eyes Closed

Left Lateral Position: Eyes Closed

Left Lateral Position: Eyes Closed

Vertebral Artery Test

1. Avoid Basilar Stroke. 2. Differential diagnosis.

Rationale

Procedure 1. Sitting or Supine. 2. Patient turns head. 3. Hyper-extension of neck and posterior head pitch.

Vertebral Artery Test

The Dix-Hallpike Maneuver:

• Detection of BPN.

• Positioning: from sitting to head hanging R or L.

• Shows Benign Paroxysmal Positional Vertigo (BPPV)

• then back to sitting.

BPPV: 

• Rotary/torsional movement• latency: ~~10 sec• fatigues within 30 to 45 sec• usually beating to lower ear.• accompanied by vertigo• R, L, or in both positions

BPPV:

• A very common finding.Etiologies:• Canalithiasis: presence of free-floating otoliths in

the Post. SCC• Cupulithiasis: otoliths adhering to the cupula of

the Post. SCC

Caloric Testing

• Via Water or Air• Right Cold 30º C. 24 º C.• Left Cold 30º C. 24 º C.• Left Warm 44º C. 50 º C.• Right Warm 44º C. 50 º C.• Wait 5 mins in between, 10 between LC and LW• Recheck Calibration in between.• Eyes closed first 1-1\2 mins then open for 10 secs.

Calorically Induced Nystagmus

Right Warm

Right Cool

Left Warm

Left Cool

COWS:

• Warm builds cupulopetal flow

• Thus, nystagmus beats

toward warm ear, away from cold ear.

• Cold- beats to the opposite side.

• Warm- beats to the same side.

Cold-Opposite-Warm-Same

Measures of Caloric Strength:

• Duration: onset of irrigation to last beat (200 secs)

• Frequency of most intense nystagmus(?Beats/sec)

• Speed of slow phase at most intense part (10 - 80)

Caloric Response Analysis:

• Unilateral Weakness: best index of periph lesion

(RC + RW) - (LC + LW) / (Sum of All 4)

> 0.25

• Directional Preponderance: of little dx value

(RW + LC) - (RC + LW) / (Sum of All 4)

> 0.35

An Abnormal

Set of Results

Can you tell

where the

problem is just

by eyeballing it?

RW

LW

LC

RC

Calculations from the

previous slide…

Unilateral Weakness(40 + 46) – (13 + 12) / 111 = 55% on the Left

Directional Preponderance(40 + 12) – (13 + 46) / 111 = 6% on the Left

More Caloric Analysis:

• Bilateral weakness: Avg response less than 6 deg/sec OR total of less than 20 deg/sec

• Fixation Index: Eyes Open / Eyes Closed*

> 0.60 = Lack of fixation: CNS lesion.

*(speed with eyes closed just prior to eyes open)

Normal Fixation Suppression

• Nystagmus is normally reduced with vision by at least 40%, commonly more.

Eyes

Open

Failure of Fixation Suppression

• Eyes closed: 24°/s

• Eyes open: 24°/s

• Fixation Index = 1.0Eyes Open

Premature Caloric Reversal: CNS lesion.

• if before 140 s,

• and speed > 6-7 deg/sec

• must be distinguished from resumption of a pre-existing nystagmus. 

Caloric Inversion, Perversion:

• Inversion: entire response beats wrong direction– TESTER ERROR– BRAINSTEM LESION

• Perversion: vertical or oblique nystagmus.– BRAINSTEM LESION