Is there a word or phrase for someone who has difficulty telling his right side from his left side?

There is the colloquial phrase directionally challenged for someone who confuses their right and left.

1. Someone who has difficulty determining right from left

2. Someone who often confuses directions, and prefers visual aids.

3. Someone who has great difficulty reading maps and/or driving while listening to directions.

[urbandictionary]

Bonus article: 25 Problems All Directionally Challenged People Can Relate To [buzzfeed]

There is also the phrase "Your other left" in slang. It is not used to define someone but used mockingly when someone confuses their right and left.

Sarcastic phrase; used with the directionally challenged to make them aware of their error.

[urbandictionary]

Further explanation:

Neuroscientists call this phenomenon as left-right confusion (or right-left confusion/disorientation). It is believed that there are neurophysiological explanations or it can be even related to your personality.

• While there’s actually no definitive answer yet, executive director of the Handedness Research Institute M.K. Holder believes the problem resides in the degree a brain function is “lateralized”, or divided between hemispheres. This explains why women and left-handed people are more likely to have this peculiarity. Men and right-handed people tend to be more strongly lateralized than do women or left-handed people. To put it simply, the more “biased” the brain is towards one hemisphere over the other; the more likely there is to be left/right confusion.¹

• OR, as one more intriguing theory suggests, your left/right confusion may just be due to your SF or NT type personality! As, Phillippe De Sainte Maresville, a Jungian expert with a left/right problem points out, “A researcher told me: “Don’t worry, you’re SF. It comes with the SF package. It is normal. It sometimes may also occur with NTs.” He believes people that combine the (S)ensing method of gathering information and the (F)eeling process of decision making are more prone to this problem of left/right confusion.¹

It is also mentioned that the brain region called parietal lobe (specifically left perietal lobe) plays a role in this phenomenon. This region is responsible for spatial sense and navigation (proprioception) and sense of touch (somatosensation).³ It is said that if you are one of the 20% that has a problem detecting left from right, you may very well have the other problems associated with the left parietal lobe.¹

_Sources:

<sub>1. "Left or Right? Why Some Smart People Confuse Them" By Erin Froehlich [smartlivingnetwork]
2. "Can't tell your left from your right? You needn't worry about it" By Susan Perry [minnpost]
3. Perietal lobe [wikipedia]</sub>