Unilateral EEG sweat artifacts in a patient of brainstem hemorrhage with central Horner's syndrome

Abstract

We present an interesting EEG finding of persistent unilateral sweat artifacts in a 47 years old male patient with right hemiplegia secondary to left thalamic bleed with extension of hemorrhage into the left internal capsule, the left midbrain and ventricles. The EEG was done for altered sensorium. It showed unilateral (right sided) sweat artifacts throughout the EEG recording. The anhydrosis on left side of the face was due to left sided Horner's syndrome because of involvement of first order neurons in the left midbrain. This EEG finding is highlighted because of it being relatively less common but interesting finding.

Keywords

Sweat Artifact - Horner Syndrome - EEG artifact

1

Case study

A 47 years old man, under regular treatment for hypertension presented to our institute with complaints of sudden onset drowsiness, right-sided weakness and slurring of speech. On examination, patient was drowsy but arousable with verbal commands. He had right-sided UMN facial weakness, right hemiparesis and hypoesthesia and right Horner's syndrome (right sided ptosis, miosis, enophthalmos and anhydrosis). He was detected to have acute intraparenchymal hemorrhage measuring 2.8 × 2.18 cm in left thalamic region extending into posterior limb of internal capsule, left side of midbrain with intraventricular extension into the third ventricle, dependent occipital horn of bilateral lateral ventricles and fourth ventricle ([Fig. 1a,b]).

Fig. 1– Case no. 1 – longitudinal montage EEG showing generalized burst of irregular, high amplitude spikes slow wave discharges lasting for 3–4 s and more regular 3 Hz spike wave discharges toward the end (black arrows). Paper speed 30 mm/s, sensitivity 15 μV/mm.

He was admitted to neurointensive care unit. Post stabilization patient was shifted to ward. While in ward, because of fluctuating sensorium patient was advised electroencephalogram (EEG) to rule out intermittent seizures or nonconvulsive status epilepticus.

His EEG showed exclusive right-sided sweat artifacts in the form of roughly 0.5 Hz medium amplitude waves ([Fig. 2a]). Another EEGs done next day had the similar findings ([Fig. 2b]). Patient had clinical features of left sided Horner's syndrome. The anhydrosis over left side of face lead to absence of sweat artifacts on left side.

Fig. 2– Case no. 2 – longitudinal montage EEG showing bursts of brief generalized spike wave discharges with 2.5–3 Hz frequency (black arrows). Paper speed 30 mm/s. Sensitivity 30 μV/mm.

2

Discussion

Although EEG is aimed at recording the cerebral activity to look for any evidence for epileptiform discharges, it is not uncommon to find various artifacts during EEG recordings particularly if it is done at bed side. One of them is sweat artifacts which can be seen as low amplitude irregular asymmetrical extremely low frequency (usually 0.25–0.5 Hz) waveforms oscillating across the baseline. Sweat leads to slow shift of electrical baseline by changing the impedance between the electrode and skin.[1] It also loosens the contact between the electrode and skin. These artifacts are intermittent and usually bilateral but they can be found unilaterally also. Lowering the room temperature and wiping the area with ether or alcohol can reduce the sweating and prevent sweat artifacts.

Unilateral sweat artifacts persisting throughout the record is a less common finding and is peculiar to Horner's syndrome. In our patient, right sided sweat artifacts were seen throughout the recording. Absence of sweat artifacts on left side was secondary to anhydrosis caused by left Horner's syndrome. Other medical causes of unilateral sweating are underlying collection (e.g. subgaleal hematoma) in or under the skin, Harlequins syndrome,[2] localized unilateral or segmental hyperhydrosis,[3] Frey's auriculotemporal syndrome[4] and Ross syndrome.[5]

3

Conclusion

We hereby report an interesting EEG finding with unilateral sweat artifacts in relation to Horner's Syndrome.

Conflicts of interest

The authors have none to declare.

No conflict of interest has been declared by the author(s).

• References

• 1 Klass DW. The continuing challenge of artifacts in the EEG. Am J EEG Technol 35 1995; 239-269
• 2 Lance JW, Drummond PD, Gandevia SC, Morris J. Harlequin syndrome: the sudden onset of unilateral flushing and sweating. J Neurol Neurosurg Psychiatry 51 1988; 635-642
• 3 Yadalla HKY, Ambika H, Chawla S. A case of idiopathic unilateral circumscribed hyperhidrosis. Indian J Dermatol 58 (02) 2013; 163
• 4 Prattico F, Perfetti P. Frey's Syndrome – images in clinical medicine. N Engl J Med 355 2006; 66
• 5 Yasar S, Aslan C, Serder ZA, Demirci GT, Tutkavul K, Babalik D. Ross syndrome: unilateral hyperhidrosis, Adie's tonic pupils and diffuse areflexia. J Dtsch Dermatol Ges 8 (12) 2010; 1004-1006

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