Crazy anxiety with unilateral weakness and fasciculations 29m

I’m a 29M in the UK, previously healthy and active, but I’ve been dealing with persistent neurological and cognitive symptoms primarily affecting the left side of my body. Over the past year, I’ve had difficulty finding words (especially nouns), issues with planning, and occasional dizziness when standing up. My sleep is disrupted with 2-4 unexplained wakeups every night, and I have an overactive bladder that wakes me 1-2 times a week to urinate.

The neurological symptoms started in September 2024 with sharp pain (7/10) in my left thigh during weight-bearing activities. This evolved into a dull ache (~5-7/10), which is triggered by high-impact exercise like running. An MRI ruled out bone involvement, and doctors now suspect the pain may involve my nervous system. A DEXA scan showed ~300g less muscle in my left leg compared to my right, and I’ve noticed that my exercise tolerance has gradually decreased. Pain temporarily improves with rest but recurs strongly after activity. Historically, my left leg was larger and dominant, but now it shows visible muscle shrinkage.

Around the same time, I started experiencing weakness and stiffness in my left arm and hand, along with occasional clawing of my ring and pinkie fingers. My grip strength has dropped to 40-45kg (down from 55-60kg and weaker than my right hand, which is 50-60kg). Fasciculations began in my left hand and have since spread throughout my body, occurring 20-100 times daily. These are brief, localized twitches that are more frequent after exercise. Resting and intention tremors occasionally occur in my left hand, and the entire arm feels persistently "off," recovering poorly after use. There’s visible muscle shrinkage in my left arm as well. There's no clinical weakness in either my left arm or my left leg (yet).

I’ve also been dealing with frequent myoclonus, where sudden jerks disrupt my sleep. These are strong enough to move my limbs or, occasionally, my whole body, and they happen mostly at rest. I’ve noticed bulbar symptoms as well, like a globus sensation, a compulsion to yawn that isn’t satisfied by yawning, and a scratchy, tight voice that worsens with anxiety. Over the past six months, I’ve felt clumsier than usual and occasionally experience mild cramping and increased sweating, but I haven’t noticed significant sensory changes, spasticity, or systemic issues.

Despite extensive testing, the cause of these symptoms remains unclear. Full-body, brain, and spine MRIs, as well as EMG and nerve conduction studies, were all normal (I've read this can happen though in early ALS). My CK levels are elevated (~190 vs. my baseline of ~90), and my reflexes are normal. Thyroid & vitamin blood tests normal. While anxiety seems to make the symptoms worse, they don’t disappear when I’m calm.

Currently, the symptoms persist but vary in intensity. Left-side pain and weakness limit my physical activity (I can still do some exercise, but running for more than 10 mins is very painful), and the fasciculations and myoclonus make daily life and sleep difficult. I’m not sure what to make of all this. Does anyone think this could still be ALS, or is it more likely something functional / another explanation?

If anyone's super interested, an elaborated case description can be found here: https://docs.google.com/document/d/1E0DmLAl5vMgEduJObOpNyK4xU47jMzHGjk0FXUS1t78/edit?tab=t.0