Prolonged administration of streptomycin may result in damage to the:
Optic nerve
Facial nerve
Auditory nerve
Trigeminal nerve
Streptomycin (antitubercular) causes vestibular damage on prolonged use.
Adverse effects

This class of drugs is notorious for their adverse effects like ototoxicity and nephrotoxicity.
About 1/5th patients given streptomycin 1 gm BD i.m. experience vestibular disturbances although auditory disturbances are less common. 
Streptomycin has the lowest nephrotoxicity among aminoglycosides; probably because it is not concentrated in the renal cortex.

Reference: Essentials of Medical Pharmacology Eighth Edition KD TRIPATHI page no 94,798